Substantia. An International Journal of the History of Chemistry 5(1) Suppl.: 99-114, 2021 Firenze University Press www.fupress.com/substantia ISSN 2532-3997 (online) | DOI: 10.36253/Substantia-1281 Citation: D.E. Moser (2021) Crystalline Stenonian Time Features from Earth and Beyond. Substantia 5(1) Suppl.: 99-114. doi: 10.36253/Substantia-1281 Copyright: © 2021 D.E. Moser. This is an open access, peer-reviewed article published by Firenze University Press (http://www.fupress.com/substantia) and distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distri- bution, and reproduction in any medi- um, provided the original author and source are credited. Data Availability Statement: All rel- evant data are within the paper and its Supporting Information files. Competing Interests: The Author(s) declare(s) no conflict of interest. Crystalline Stenonian Time Features from Earth and Beyond Desmond E. Moser Department of Earth Sciences, University of Western Ontario, London, Ontario, Canada; N6A 5B7 E-mail: desmond.moser@uwo.ca Abstract. The writings of Niels Stensen (Steno) on mineral growth and modification in his Prodromus, together with his work on time and process in other solids, are here synthesized as five classes of time features defined by changes in the visible continu- ity of either or both chemistry and orientation. This organization highlights Steno’s implicit recognition of the fractal, scale-invariant nature of natural time features with regard to space, time, and material. The effectiveness of this Stenonian geochronology framework is demonstrated down to atom scale with modern case studies of the U-Pb geochronology of mineral zircon in samples originating from the Earth, Moon, and Mars spanning most of solar system history. Recently discovered nano-scale features, here termed chronostructures, were intimated by Steno in his corpuscular view of mineral behaviour. The remarkable advances in the Prodromus are seen here as result- ing from the intersections of Steno’s highly attuned approach to visual perception, his adoption of Stoic (Senecan) ethics early in his career to guide his natural philosophy, and the influence of the Galilean scientific environment of Florence. It is argued that the scale-invariant, intensive quality of Stenonian geochronology makes it an invalu- able check on the accuracy of absolute, extensive measurements of geologic time by chemical or isotopic means. In this way Steno’s scientific legacy continues to propel human understanding of how we see our place in time. Keywords: Steno, crystal, zircon, geochronology, fractal, Stoic. 1. INTRODUCTION: The geological writings of the famed anatomist Niels Stensen, most- ly expressed in his “The Prodromus to a Dissertation on a Solid Naturally Contained Within a Solid” (hereon referred to as the Prodromus),1 have been seen as foundational to the current fields of stratigraphy, palaeontology and crystallography through his elucidation of the principles of sedimenta- ry superposition, the organic origin of fossils, and the law of angular con- 1 N. Stensen, De Solido Intra Solidum Naturaliter Contento Dissertationis Prodromus, Florence, Stella, 1669 (Prodromus in following notes). English translation in T. Kardel, P. Maquet, Nicolaus Steno, Biography and Original Papers of a 17th Century Scientist, 1st edition, Heidelberg, Springer, 2013 (K&M in notes below), pp. 621-660, 100 Desmond E. Moser stancy in crystals, respectively. Steno’s ‘founder’ sta- tus, however, is seen by some historians of science as anachronistic,2 given that his authorship of these ideas was ignored for more than a century before acknowl- edgement in later retrospectives of geography and geology.3,4 More recent historians of science have com- mented that Steno’s Prodromus was principally an advance in the cognition of geologic time.5,6 Steno’s novel and detailed descriptions of mineral growth have received renewed attention7, and in this paper I propose that his influence on the field of geochronology like- wise merits greater recognition, particularly in light of the continuing application of Stenonian methods. With Steno’s mineralogy as a starting point, I have used his observations of time information in all solids to derive a classification scheme for Steno’s vision-based geochro- nology. The modern relevance of this scheme is illustrat- ed with microscopy case studies, down to atom scale, of the weakly radioactive geochronology of mineral zircon in samples from Earth and other planetary bodies span- ning most of solar system history. This is followed by a consideration of Steno’s method of observational science in the context of his European education and association with the Galilean Accademia del Cimento to explore rea- sons why Steno was able to perceive geologic time hid- den from most others. Finally, the continuing impor- tance of Steno’s approach to the accuracy of both rela- tive and absolute geochronology is discussed. It is hoped that, as it did for me, this treatment links Earth scien- tists and geochronologists more clearly to our observa- tional and philosophic roots as well as to an awareness of the 17th century brilliance of Steno working in the Galilean tradition. Relative and absolute geochronology - then and now Geochronology is taken here to be the science of measuring time information from natural materials and 2 M. J. S. Rudwick, The Meaning of Fossils. Episodes in the History of Pal- aeontology. London, MacDonald, London, & New York, American Else- vier Inc., 1972, 287 pp. 3 N. Desmarest, Géographie physique. 4 vols. Paris, 1794 [Encyclopédie méthodique]. 4 C. Lyell, Principles of Geology: being an attempt to explain the former changes of the Earth’s surface, by reference to causes now in operation. London, John Murray, 1, 1830. 5 K., von Bülow (1971) Stenos aktualistisch-geologische Arbeitsweise, Scherz, Dissertations on Steno as Geologist. Acta Historica Naturalium et Medicinalium, 1971, 149–162; as cited in ref. 1 (K&M). 6 S. J. Gould, The titular bishop of Titiopolis. Natural History, 1981, 90, pp. 20–24; reprinted in Hen’s teeth and horse’s toes, New York, Norton’s Paperback, 1983, pp. 69–78. 7 A. Authier, Early Days of X-ray Crystallography. International Union of Crystallography/Oxford University Press, 2013, pp. 299-305. to be of two types; relative, establishing the numeri- cal order of events, and absolute, the age of an event or interval referenced to units of years. In the age of Steno, and particularly in the Prodromus, the relative and abso- lute times for events in Earth history were based on nat- ural philosophy and biblical scripture, respectively, and were not seen to intersect or conflict as they were deriva- tives of independent logic systems2,8 with which Steno presented faith and natural history as separate domains of knowledge.9 Steno’s natural philosophy was likely influenced by that of Aristotle, in view of his adaptation of Aristotelian form and argument in his early work on hot springs, De Thermis10. Sambursky provides a concise summary of Aristotelian philosophy regarding relative and absolute time: Aristotle’s definition “time is number of motion in respect of ‘before’ and ‘after’”—expresses both the association of time with change and the possibility of enumerating this change. It is also evident from his analysis that he realized that the prerequisite for time measurement is a clock, i.e., a periodic mechanism, and that the revolution of the celestial sphere, being a regular circular motion, is the best measure of time “because the number of it is the best known”.11 As noted by many authors, Steno declined assigning absolute ages directly to natural solids as on this topic “nature says nothing”,12 but he nevertheless played a pio- neering role in ordering sedimentary strata in respect to the directional arrow of time.13 The 19th century saw the ascendence of absolute geochronology after the discovery of the laws of radio- activity and techniques for measuring ratios of ele- ments and their isotopes in rocks and minerals.14 The first measurement of the absolute ages of sedimentary strata is widely attributed to Holmes15 who compared 8 A. H., Cutler, Nicolaus Steno and the problem of deep time, in The Revolution in Geology from the Renaissance to the Enlightenment (Ed. G. D. Rosenberg), Geological Society of America Memoir, 2009, 203, p. 143–148. 9 J. Bek-Thomsen, Steno’s Historia. Methods and Practices at the Court of Ferdinando II, in Steno and the Philosophers (Eds.: R. Andrault, M. Lærke), Brill, Leiden, 2018, p. 233-258. 10 R. Rappaport, When geologists were historians, Ithaca and London, Cornell University Press, 1997, 320 pp. 11 S. Sambursky, Physics of the Stoics. Princeton, NJ, Princeton University Press, 1987, 166 pp. 12 N. Stensen, Prodromus, in ref. 1 (K&M), p. 654. 13 G. Kravitz, The geohistorical time arrow: from Steno’s stratigraphic principles to Boltzmann’s past hypothesis, Journal of Geoscience Educa- tion, 2014, 62, p. 691-700. 14 E. Rutherford, E., & F. Soddy, J. Chem. Soc., 1902, 81, p. 837; reprint- ed in Phil. Mag., 1902, 4, p. 370; 1903, 5, p. 576. 15 A. Holmes, The association of lead with uranium in rock-minerals, and its application to the measurement of geological time. Proceedings of the Royal Society of London A, 1911, 85, p. 248-256. 101Crystalline Stenonian Time Features from Earth and Beyond the relative (Stenonian) geochronology of a section of early Paleozoic sediments in Norway to absolute ages calculated from the U and Pb abundances in miner- als (including zircon (ZrSiO4)) from inter-layered and cross-cutting igneous (once molten) rock bodies. Criti- cally, Holmes established the premise of the “closed system” for absolute methods; stipulating that an age measurement is only accurate if the sampled volume has remained closed to chemical alteration since its produc- tion aside from change due to radionuclide decay. In this light, and in the terminology of thermodynamics, every absolute geologic age is an extensive property of a solid. The extent of the systems in Holmes’ pioneering work were mineral grains containing U and its radio- genic Pb. As we will see, it is due to this extensive prop- erty that the accuracy of absolute methods relies, ulti- mately, on Steno’s relative approach. Minerals are defined by the International Miner- alogical Association as the inorganic building blocks of rocks, each characterized by a particular chemical composition and a defined crystal structure. These com- monly occur as polyhedral bodies such as the cm-scale specimens described in the Prodromus. Steno classed minerals as “angular solids”, and focused on samples of “crystal” (quartz) and “iron” (hematite, pyrite) which he collected from the Tuscany region, Elba, and other localities in central Europe16. Absolute geochronology using the U-Th-Pb decay chains has become the bench- mark for calibrating the time scale for the Earth17 and solar system,18 and the U-bearing mineral zircon plays a major role.19 Zircon occurs widely in the crusts of rocky planets, mostly as microscopic grains forming accessory compo- nents in rocks over a depth range on the order of 100 kilo- metres. The primary features of each grain can withstand erosion, mountain building events, transport in magmas, plate tectonic cycles, and meteorite impacts; all the while accumulating either or both external and internal fea- tures that bear witness to these events.20 Zircon crystals commonly have the width of a human hair, an order of magnitude smaller than Steno’s cm-scale samples (Fig. 1), yet zircon grains have the distinction of being the old- 16 N. Stensen, in ref. 1 (K&M), p. 208. 17 Y., Amelin, et al., Lead isotopic ages of chondrules and calcium-alu- minum-rich inclusions. Science, 2011, 297, pp. 1678-1683. 18 J. M. Connelly et al., Chronology of the solar system’s oldest solids. The Astrophysical Journal, 2008, 675, p. L121–L124. 19 B. Schoene, U–Th–Pb Geochronology, in Treatise on Geochemistry, K. Turekian, H. Holland (Eds.), 2014, 4, Elsevier Oxford, p. 341-378. 20 F. Corfu, J. M. Hanchar, P. W. O. Hoskin, P. Kinny, Atlas of zircon tex- tures. Reviews in mineralogy and geochemistry, 2003, 53, p. 469-500. est known pieces of the Earth,21 Moon22 and Mars.23 Zir- con also has a different crystal structure in comparison to Steno’s quartz (tetragonal vs. hexagonal) however it exhib- its a similar, long-prismatic habit such that it is weakly to strongly columnar, sharing “intermediate” (prismatic) and “terminal” (pyramidal) faceting reported by Steno.24 Zir- con exhibits internal zoning when a cross-sectional sur- face is imaged with a scanning electron microscopy and a cathodoluminescence detector (SEM-CL).25 These zones are analogous to the colour changes noted by Steno in his quartz cross sections of “the plane in which the axis of the crystal lies”26 (Fig 1). Steno’s cross-sectional depictions were novel in his time, marking a transition from ‘organic’ to ‘mechanical’ mineralogy’,27 whereas such cross-sectional crystal imaging is now a routine component of petrology and absolute zircon geochronology. Previous work on Stenonian geochronology The framework which Steno describes in the Pro- dromus for interpreting the Earth resolved not only the immediate question of the nature of fossils, and dis- criminating their found location from their place of production, but presented a logic structure for identify- ing geologic time sequences from features discernible in solids.28 Steno’s authorship of this structure was largely ignored among later theories of the Earth although his concepts and ideas carried on in the work of others such as Leibniz29 or were tested and transmitted by later Ital- ian geologists.30 Receiving most attention was his princi- 21 J. W. Valley, A. J. Cavosie, T. Ushikubo, D. A. Reinhard, D. F. Law- rence, D. J. Larson, P. H. Clifton, T. F. Kelly, S. A. Wilde, D. E. Moser Hadean age for a post- magma-ocean zircon confirmed by atom-probe tomography. Nature Geosci., 2014, 7, p. 219–223. 22 A. Nemchin, N. Timms, R. Pidgeon, et al. Timing of crystallization of the lunar magma ocean constrained by the oldest zircon. Nature Geosci., 2009, 2, p. 133–136. 23 L. C. Bouvier et al., Evidence for extremely rapid magma ocean crys- tallization and crust formation on Mars. Nature, 2018, 558, p. 586–589. 24 N. Stensen, in ref. 1 (K&M), p. 639. 25 J. M. Hanchar, C. F. Miller, Zircon zonation patterns as revealed by cathodoluminescence and backscattered electron images: implications for interpretation of complex crustal histories. Chemical Geology, 1993, 110, p. 1-13. 26 N. Stensen, in ref. 1 (K&M), p. 659. 27 W. R. Albury, D. R. Oldroyd, From Renaissance mineral studies to historical geology, in the Light of Michel Foucault’s “The Order of Things”. The British Journal for the History of Science, 1977, 10, pp. 187- 215. 28 M. J. S. Rudwick, The meaning of fossils. Episodes in the history of pal- aeontology. London, MacDonald, London, & New York, American Else- vier Inc., 1972, 287 p. 29 D. Garber, Steno, Leibniz, and the history of the world, in ref. 8, p. 201-232. 30 S. Dominici, Steno, Targioni and the two forerunners. Journal of Med- iterranean Earth Sciences, 2009, 1, p. 101-110. 102 Desmond E. Moser ple of ‘moulding’31 which had been denoted in the 18th century by Desmarest as Steno’s “Premier Principé ”. 32 Among the most detailed modern assessments of Steno’s work regarding relative geochronology is that of Hans- en33 who recognized in Steno’s writings the “cognition criteria” of chronology, recognition (i.e. resemblance), and preservation. Chronology was subdivided into the principles of moulding and intersection. Moreover, two underlying axioms related to the quality of orientation were proposed in terms of “conformity,” and “discon- formity.” Steno’s interpretation of what had been viewed previously as “signs” in natural materials34 were termed “structural”, underpinning a further five principles of geological interpretation leading to “back-stripping” to reconstruct crustal dynamics over time. These organiza- tions of Steno’s work on solids were interpreted predom- inantly from his macroscopic observations of sediments, and, while valid and self-consistent, did not incorporate many of Steno’s observations of minerals and mineral- ized bodies such as agate (“incrustations”). When these too are considered, and paired with Steno’s atomistic (corpuscular) view of crystals,35 additional Stenonian insights become apparent. 2. METHOD AND MATERIALS The Prodromus has been called “a complex and odd little book ”,36 and in his introductory text Steno does apologize to his patron for any seeming disorganization due to the constraints of time and travel. My analysis initially relied on the English translation of the Prodro- mus by Winter37, but then mainly fell to translations of the much broader compilation of Steno’s works translat- ed by Kardel and Maquet,1 all of which were approached in several ways. First, all indications, whether in the text or diagrams, of time, motion, and process observed or deduced from natural solids, were noted with particular 31 S. J. Gould, S.J. in ref. 6. 32 N. Desmarest in ref. 3. 33 J. M. Hansen, On the origin of natural history: Steno’s modern, but forgotten philosophy of science, in ref. 8 (Rosenberg), p. 159-178. 34 T. Yamada, Kircher and Steno on the “geocosm”, with reassessment of the role of Gassendi’s works, in The origins of geology in Italy (Eds. G. B. Vai, W. G. E. Caldwell), Geological Society of America Special Papers, 2006, 411, p. 65–80. 35 W. C. Parcell, Signs and symbols in Kircher’s Mundus Subterraneus, in ref. 7 (Rosenberg), p. 63-74; C. J. Schneer, Steno on crystals and the cor- puscular hypothesis, dissertations on Steno as geologist. Acta Historica Naturalium et Medicinalium, 1971, 34, p. 293–307. 36 R. Rappaport, in ref. 10, p. 202. 37 J. G. Winter, The prodromus of Nicolaus Steno’s dissertation concerning a solid body enclosed by process of nature within a solid. University of Michigan studies: Humanistic series, Macmillan, 1916, 115 pp. attention to Steno’s descriptions of minerals and incrus- tations in the Prodromus. The visual-cognition term ‘feature’ (see definition below) was then used to subdi- vide Steno’s descriptions of temporal phenomena into classes according to chronology, process, and underly- ing material properties causing continuity, or disruption, of either or both chemistry and geometric orientation (Table 1). The sources of translated Steno quotes in Table 1 regarding Minerals and Strata occur in the main body of text, whereas the remainder are as follows for Fossils38 and Incrustations.39 Note that the S5 class descriptor is based on a translation from Hansen (2009) in Ref. 8. Detailed class descriptions with relevant translations of Steno are presented alongside modern microscopy results for the U-Pb geochronology of the mineral zir- con. All microscopy was performed by the author’s research group and collaborators using previously described electron beam techniques40 at the University of Western Ontario or using previously described atomic imaging techniques41,42 at the Canadian Centre for Elec- tron Microscopy, McMaster University. Terminology for Stenonian time features The term feature has been used here to general- ize the different signs or visual patterns which Steno ascribed to the effects of time’s passage during the pro- duction or alteration of solid materials. Steno’s raw vis- ual observations are mostly expressed as geometric sur- faces, with the word ‘surface’ here used according to the mathematical definition; a generalization of all planes which may or may not have some amount of curvature. Steno’s geometric descriptions of surfaces in the Prodro- mus followed either Euclidean geometry or projective geometric representations of the Platonic solids in the tradition of Pierro, Kepler and Dürer,43 and his single plate of diagrams44 combines these approaches. Notably, 38 N. Stensen, in ref. 1 (K&M), p. 647-648. 39 N. Stensen, in ref. 1 (K&M), p. 630. 40 D. E. Moser, C. L. Cupelli, I. R. Barker, R. M. Flowers, J. R. Bowman, J. Wooden, J. R. Hart, New zircon shock phenomena and their use for dating and reconstruction of large impact structures revealed by elec- tron nanobeam (EBSD, CL, EDS) and isotopic U-Pb and (U-Th)/He analysis of the Vredefort dome. Can. J. Earth Sci., 2011, 48, p. 117-139. 41 J. R. Darling et al., Variable microstructural response of baddeleyite to shock metamorphism in young basaltic shergottite NWA 5298 and improved U-Pb dating of Solar System events. Earth Planet. Sci. Lett., 2016, 444, p. 1-12. 42 G. A. Arcuri, D. E. Moser, D. A. Reinhard, D. Larson, B. Langelier, Impact‐triggered nanoscale Pb clustering and Pb loss domains in Archean zircon. Contributions to Mineralogy and Petrology, 2020, 175, p. 59, 1-13. 43 C. J. Schneer, in ref. 35. 44 N. Stensen, in ref. 1 (K&M), p. 658. 103Crystalline Stenonian Time Features from Earth and Beyond and, perhaps unique for his time, are his two-dimen- sional projections and juxtaposition of three-dimen- sional geologic entities, such as sedimentary strata and growth layers within crystals, into a Euclidean plane which contains either the downward vector of Earth’s gravity or the principal (central) axis of crystal growth. Steno does not refer to most of these features in formal geometric terms but as nouns with embedded actions. He does not, for instance, refer in Latin to a sedimentary deposit as a planum (plane), but as a stratum- the past participle of sternere “to spread out”. Action, motion, and thus time, thereby become embedded meanings in his descriptor of a planar, natural feature. Some have referred to parts of Steno’s drawings as “structures”, particularly the ruptured strata in his cross-sections of Tuscany;45 however, this term derives from structus, the past participle of struere “to pile,… assemble”, whereas, at mineral grain or crystal lat- tice scales, these features are more accurately described by voids or a breakdown of order. As discussed below, Steno’s methods are primarily visual, and consequently the visual term ‘feature’ is adapted here to encompass true structures and other types of recognizable mate- rial changes in solids. A ‘ feature’, when used in regard to material objects, is defined in English as “some part which arrests the attention by its conspicuousness”.46 Time is implicit in this definition - not in regard to the passage of time during production of the object but of time elapsing during the act of its observation dur- ing which the mind’s attention is arrested. This process of observation will be discussed later in the context of Steno’s methodology. 4. RESULTS Upon consideration of Steno’s observations of all natural solids, five classes of Stenonian time features signifying production or modification can be described, along with a brief mention of a sixth ‘origin’ class (Table 1). The first two classes of Stenonian time features can be considered as one or more Euclidean planes in that they, at length scales of observation typical in geol- ogy, are surfaces with zero curvature at any point. For Steno’s “crystals” the planes in his diagrams are two- dimensional projections of symmetrically-related set of crystal facets analogous to sedimentary strata (Fig. 1). Together they are the primary features of production and establish the reference features for discriminating 45 J. M. Hansen in ref. 33. 46 “feature, n.” OED Online, Oxford University Press, December 2020, www.oed.com/view/Entry/68848. later, modifying processes and events. The other three feature classes represent, at some scale, disruptions in continuity; what Steno described in the case of tilted strata as “obvious inequalities” 47 of angle with respect to the horizon and the gravitational field. At the atomic level in minerals, such discontinuities fall into two broad groups: discontinuity in chemistry, while maintaining crystalline order, and discontinuity due to a breaking or re-orienting of atomic bonds without necessarily chang- ing the chemical composition. Each class is denoted with “S” for Steno and a subscript identifying the class num- ber, and is described along with comparable features in zircon crystals. a) S0, S1 Features representing growth, hiatus, envi- ronmental change With regard to the beginning of the formation of a solid, Steno acknowledges that such a place must exist but would not speculate further. For minerals he stated that: “There may still be doubt about the place in which the first crystal begins, whether it be between fluid and fluid or between fluid and solid or in fact in a fluid by itself ”,48 and strata are described only as being preceded by a global fluid. Nevertheless Steno acknowledges the existence of a beginning point and it is represented in this scheme as S0, the first point of production which, for minerals, is taken as the geometric centre of zoning (Fig. 1). From there he recognized, in different places in his writings on solids, subclasses of S1 features to which he attributed vectors, pauses, and environmental changes during production. Vectors and nature of growth processes Steno’s view of mineral growth shared some simi- larities with sedimentary strata but with important dif- ferences in the kinetics of growth. In both solids he saw that; “The growth of all solids is from fluids” and that a body “grows by addition of new particles”.49 Hearken- ing to his choice of the term stratum for sedimentary layers, Steno indicates that “new crystalline material, added to the crystal, is spread out over a plane”50 with the important difference that “buoyancy or gravity are not involved”,51 and crystal growth is instead driven by “the subtle fluid permeating all matter”52. Thus gravity controls sedimentation in a single, vertical field, whereas particle addition in another field causes crystals to grow 47 N. Stensen, in ref. 1 (K&M), p. 653. 48 N. Stensen, in ref. 1 (K&M), p. 639. 49 N. Stensen, in ref. 1 (K&M), p. 630. 50 N. Stensen, in ref. 1 (K&M), p. 642. 51 N. Stensen, in ref. 1 (K&M), p. 634. 52 N. Stensen, in ref. 1 (K&M), p. 631. 104 Desmond E. Moser along several, mathematically related directions. Steno analogized crystal growth with particles aligning like iron filings in a magnetic field such that “both the num- ber and length of the sides are changed in various ways without the angles being changed.”53. Flow in the min- eral’s parent liquid did not alter the direction of the field driving crystallization in that “the movement of crystal- 53 N. Stensen, in ref. 1 (K&M), p. 642, also ref. 41. line material […] depends on the movement of the tenu- ous fluid that flows from the already formed crystal”. 54 Successional growth Among the most important spatiotemporal deduc- tions by Steno was that of the successional growth of lay- 54 N. Stensen, in ref. 1 (K&M), p. 642. Table 1. A classification scheme for Stenonian time features in solids (top row) based on representative Steno descriptions symbolized as; “quotations from Steno (transl.)”, ‘author’s condensation of translated text’, and [modern terminology]. Arrows represent cases where fea- tures in strata are now known to have analogous mineral features. *Far left column identifies the quality of the continuity change across each feature relative to its surroundings as; chemical (C) , geometric orientation (O) or a combination of either or both (C||O). See Methods for sources of translated Steno quotations. “Angular solids” [Minerals] “Strata” [Fossil] “Incrustations” [Concretions] * Stenonian time feature class C S5; intra-solid diffusion smallest particles in “inner revolt” [metamorphism] O S4; deformation (brittle, rapid) <— “shattering” causing “obvious inequalities” in angles O S4; deformation (plastic, slow) <— “subsidence”, “twisting into curves” C||O S3; mechanical erosion “fractured sides” [erosional unconformity] C||O S3; chemical erosion dissolution “cavity” leaving “lamellae” [chemical unconformity] ‘shell partly destroyed, eaten away’ C||O S2; end of production surface of “angular solid”, form related to ‘constancy of angles’ “upper surface is parallel to the horizon” final form related to gravity “outer edge of the animal” ‘outer surface of concretion’ controlled by roughness of place C S1; hiatus in production “if…crystal contained by crystal” then ”contained bodies already hard” ‘fluid recession, sediment hardening, and fluid return’ C S1; growth and environmental change during growth “crystal grows while new crystalline material is added to the already formed crystal” colour zoning due to “ingress of new material” strata differences due to “different kinds of fluid from different places through that spot at different times” ‘imprint on each margin of the testulae’ C S1; growth domain crystal layer created by “addition of new particles in succession” “stratum” “testulae” mollusc shells “fluid directs material to the solid on all sides” S0; start of production “doubt about the place in which first hardening of the crystal begins” [nucleation] “Creation from a fluid that covered all things” point of nucleation ‘seed’ 105Crystalline Stenonian Time Features from Earth and Beyond ers in solids. For minerals he noted that “crystal growth was not vegetative”55 as in herbaceous plants. His argu- ment against the vegetative mineral growth hypoth- esis can be traced to his discussion of the growth layers within the class of solids he termed “incrustations” (i.e., agates, geodes). He describes the “diff erences in layers” in these solids with the important time descriptor of rel- ative age; “succession”.56 He recognized the curviplanar geometry and extension of the concentric layers in these “stones composed of layers the two surfaces of which are indeed parallel but are not extended in the same plane”. He then compared these to the concentric, curviplanar growth layers in non-herbaceous woody plants “where they show the round veins of a tree cut transversely”.57 Steno contrasts these processes for mineralized bodies with those giving rise to strata, stating that: 55 N. Stensen, in ref. 1 (K&M), p. 640. 56 N. Stensen, in ref. 1 (K&M), p. 634. 57 N. Stensen, in ref. 1 (K&M), p. 633. Additions [of particles] made directly to a solid from an external fl uid sometimes fall to the bottom because of their own weight, as in the case of sediments; sometimes the additions are made from a penetrating fl uid that directs material to the solid on all sides, as in the case of incrus- tations.58 Th e outward growth of minerals is now universally recognized and utilized in the fi elds of petrology and mineralogy in which rocks and minerals are examined in polished, transparent sections, and likewise in zir- con geochronology where SEM-CL microscopy is used to reveal S1, concentric growth banding. Th ese repre- sent changes in trace element chemistry inherited from the magma and are expressed as variations in lumines- cent intensity and/or colour (Fig 1). Th e orientation of the crystal lattice across the chemical zoning does not change such that banding marks discontinuities in chemistry within a zone of continuous crystal orienta- tion. Time gap (hiatus) in growth “Stony strata are found between earthy strata” due to a “fl uid, having receded from the sediment that had been deposited, returned again when the upper crust had become hardened by the heat from the sun”.59 Beyond outward growth, Steno recognized that both the conditions and rate of grow th can vary during the production of natural solids. Drawing on his writ- ings on strata, he clearly envisions a scenario wherein either or both a time gap and changes in the forma- tive environment results in variations in visual prop- erties across a set of layers. In his second proposition he states, “if at any time a crystal is partly enclosed by a crystal, a marcasite by a marcasite, then at a time when these contained bodies were already hard, part of the containing body was still fl uid”.60 A correspond- ing recognition of hiatus in sedimentation was also noted as possible (above). We now know that concen- tric, apparently continuous, zoning sequences within zircon grains released from a single volcanic eruption lasting days can, in some cases, represent age diff er- ences of hundreds of thousands of years; their S1 fea- tures a product of halting outward growth over this period. Th e crystal shown in Fig.1 is representative of those from a Cretaceous ash layer, now exposed in the Canadian Rocky Mountains. Absolute dating of such grains indicates that the zoning represents up to sev- 58 N. Stensen, in ref. 1 (K&M), p. 630. 59 N. Stensen, in ref. 1 (K&M), p. 635. 60 N. Stensen, in ref. 1 (K&M), p. 629. Figure 1. Stenonian time features of production (S0, S1, S2; see text) from Plate 1 of the Prodromus1 showing a) undeformed strata (km- scale), b) growth zones in sectioned quartz (cm-scale) and c) SEM- CL image of a polished section through a zircon microcrystal (note scale bar 5 micrometre scale bar). 1 N. Stensen, in ref. 1 (K&M), p. 658. 106 Desmond E. Moser eral hundred thousands of years of crystallization prior to eruption61. Environmental change during growth Difference in layers at the same place can be produced either by the diversity of particles leaving the fluid in suc- cession, as this f luid is gradually dissipated more and more, or by different fluids being conveyed there at differ- ent times: so it happens that sometimes the arrangement of layers is repeated in the same place, and often evident signs exist showing the ingress of new material. 62 Steno was careful to distinguish “place” (i.e., the place or environment where a solid was produced) from the “location”, or site of discovery of that solid, recog- nizing that “location does not explain production”.63 In the case of strata, Steno also recognized that changes in the sedimentary section could reflect changes in sedi- mentary conditions and sources through time, and that stratal changes vertically result from “different kinds of fluid from different places through that spot at differ- ent times”. Similarly for minerals, Steno understood that the place of production imbues solids with signatures of their native environments, such that “Rocks of different types, emitting different fluids, produce crystals of dif- ferent colours”64. Moreover, Steno realized that even in the place of production, an environment of crystalliza- tion can change during the growth such that “sometimes in the same crystal the parts first hardened are some- times darker than those hardened last”.65 We now know that igneous minerals commonly show internal compo- sitional layering due to very local effects of growth-limit- ing elements among other factors such as surface energy, magma viscosity, and temperature, as is known for both quartz66 and zircon.67 b) S2 final form at end of production A second class of Stenonian time feature is defined as the exterior or upper surface of a solid at the comple- tion of its growth in the place of production. For miner- 61 I. R. Barker, D. E. Moser, S. Kamo, G. Plint, High-precision U–Pb zir- con ID–TIMS dating of two regionally extensive bentonites: Cenoma- nian Stage, Western Canada Foreland Basin. Can. J. Earth Sci., 2011, 48, p. 543–556. 62 N. Stensen, in ref. 1 (K&M), p. 634. 63 N. Stensen, in ref. 1 (K&M), p. 628. 64 N. Stensen, in ref. 1 (K&M), p. 641. 65 N. Stensen, in ref. 1 (K&M), p. 641. 66 D. A. Wark, B. E. Watson, TitaniQ: a titanium-in-quartz geothermom- eter. Contributions to Mineralogy and Petrology, 2006, 152, p. 743-754. 67 P. W. O. Hoskin, Patterns of chaos: Fractal statistics and the oscilla- tory chemistry of zircon. Geochimica et Cosmochimica Acta, 2000, 64, p. 1905-1923 als crystallizing from a liquid, S2 is a polyhedral surface composed of Euclidean planes (crystal growth facets) the orientations of which follow Steno’s law of angular constancy. Figure 2 illustrates Steno’s method of project- ing this three dimensional surface such that “all the 12 planes laid out in one plane” 68 and neighbouring crys- tal facets connected by a shared vertex. He recognized it as a time marker implicitly in his use of it to infer order of crystal growth (above). It should be noted that Steno did not consider metamorphic minerals, i.e. crystals that grew while most of its surroundings were solid. The S2 surface of such grains reflects some combination of growth processes and surface energies among surround- ing mineral phases69. In either case, the final, outer sur- face represents a discrete point along time’s arrow. This is at once the simplest and perhaps most important time feature for Steno’s interpretation of fossils as it occurs at the meeting place of an object with its surroundings (rock, air, etc.) at its present location (Table 1). The S2 feature class includes the uppermost surface of a stra- tum, the final form of an organism, or the outermost atomic layers of a crystal. This was the key time feature used to discriminate between an allocthonous (trans- ported from elsewhere) vs. autochthonous (formed in situ) origin for Steno’s fossils relative to their found loca- tion (i.e. Desmarest’s Premier Principé). This feature is of central importance in the Prodromus and remains a key tool in the modern geochronologic interpretations of minerals such as zircon as to whether or not they are endogenic or exotic to their current setting. c) S3 modifications of original form The S3 class of features, along with the other two remaining classes, share the characteristic of being sur- faces marking discontinuities in one or both of chemical composition and crystallographic (atomic) orientation, with the change occurring over a length-scale much less than that of the relevant surfaces. S3 due to chemical erosion (dissolution) just as a crystal has formed from a fluid, so that same crys- tal can be dissolved in a fluid, provided one knows how to imitate nature’s true solvent.70 Following on his basic statement that all solids grow from fluids, Steno concludes that the process can oper- ate in reverse (above). It is plausible that Steno shows 68 N. Stensen, in ref. 1 (K&M), p. 659. 69 R. Kretz, On the spatial distribution of crystals in rocks. Lithos, 1969, 2, p .39-69. 70 N. Stensen, in ref. 1 (K&M), p. 643. 107Crystalline Stenonian Time Features from Earth and Beyond the eff ects of dissolution in his Diagram 6 where he describes “that various cavities are left in the very mid- dle of the crystal and various lamellae are formed.”71 (Fig. 3). Th is diagram could be interpreted to show a partly dissolved quartz crystal with lamellae of relict growth layers (S1) from the originally continuous solid body. Alternatively, the lamellae could represent a face of relatively slow crystal growth frustrated due to surface kinetic eff ects. Regardless, it is clear that Steno antici- pated dissolution during natural processes. Resorption surfaces similar to the forms in Steno’s drawing were produced in zircon by Prof. Th omas Krogh in labora- tory etching experiments 72 and rounding of originally equant zircons due to metamorphic fl uids in the crust is now widely documented.73 Oft en this stage of resorp- 71 N. Stensen, in ref. 1 (K&M), p. 646. 72 D. W. Davis, I. Williams, T.E. Krogh, Historical development of zir- con geochronology. Reviews in Mineralogy and Geochemistry, 2003, 53, p. 145-181 73 M. J. Kohn, N. M. Kelly, Petrology and geochronology of metamor- phic zircon, in Microstructural geochronology: planetary records down to atom scale (Eds. D. E. Moser, F. Corfu, J. R. Darling, S. M. Reddy, K. T. tion is followed by renewed zircon growth continuous in lattice orientation (i.e. epitaxial growth), but diff erent in chemical composition (Fig 3). Th is creates a feature visually akin to an angular unconformity in strata, as shown in a 4.02 billion year old zircon from Earth’s old- est known rock (Fig. 3).74 S3 due to mechanical erosion “nor have I ever seen a crystal whose still unbroken surfac- es have the smoothness that the fractured sides of the same crystal show aft er it has been broken apart.”75 Steno was clear that a solid body could form in one place and move to another unrelated to its genesis: “since the earth bestows location at least in part to all Tait), Hoboken, NJ, Wiley, 2017, p. 35–61. 74 J. R. Reimink, T. Chacko, R. A. Stern, L. M. Heaman, Earth’s earliest evolved crust generated in an Iceland-like setting. Nature Geoscience, 2017, 7 , p. 529-533. 75 N. Stensen, in ref. 1 (K&M), p. 642. Figure 2. Two views of Steno’s fi nal surface of production (S2) in minerals; a) Steno’s two dimensional representation of the external, Euclidean planes of an ‘iron” crystal (marcasite) b) An SEM image of a euhedral, igneous zircon crystal, same sample as in Figure 1c (grain length = 250 micrometres). Note the mould of a smaller grain (white arrow), likely the mineral apatite, encountered during the last increment of growth before eruption. Figure 3. Features of modifi cation: a) Steno’s quartz crystal and a surface of S3 chemical dissolution. Zircon SEM-CL images showing b) 4.02 billion year S1 growth features truncated by a S3 dissolution (metamorphic) surface, c) a zircon from beach sand with external S3 surface of mechanical erosion. d) Southward view from Canada of the Niagara River Gorge and the type locality for the Silurian Whirlpool sandstone; Inset, SEM-CL image of rounded zircon sand grain among quartz grains (red), Whirlpool sandstone. All zircon grain lengths ~ 300 micrometres. 108 Desmond E. Moser the things of the earth, the location by itself does not explain the production of a body”.76 He recognized that “Mountains can be destroyed”,77 that cavities can be filled with “earthy material eroded from higher places by the continuous rainfall”,78 and that the par- ticles in sediments sink under their own weight even if “conveyed there from elsewhere”.79 In his series of strata cross-sections he notes “hills and valleys pro- duced there by the destruction of the upper sandy strata”.80These clues to motion and erosion on the outer surface of the Earth were also noted for crystals,81 and the incrustations: Incrustations are observed to be rough like ordinary stones on the outer surface, since the outer surface of the outer layer depicts the roughness of the place; in torrents, howev- er, incrustations of this kind are often found away from the place of production because the material of the place has been scattered by the bursting of the strata.82 Steno recognized the difference between growth fac- es and those modified by breakage (above) and this is a second type of intersection relationship with the original outer form or surface (S2); one that is due not to dissolu- tion of particles in a surrounding fluid but to mechani- cal abrasion or breakage during transport which modi- fies the original form causing an interruption in the con- tinuity of the internal features when viewed in section (Fig. 3). Zircon grains are extremely resistant to chemi- cal and mechanical breakdown, and the oldest known pieces of the earth are fine, sand-sized grains of zircon in much younger, though still ancient, sediments.83 e) S4 features due to episodes of deformation The earth’s strata can alter position in two ways. The first way is the violent upheaval of strata, whether this be due mainly to a sudden flare of subterranean gases or to a vio- lent explosion of air caused by other great subsidence near- by. This upward thrust of strata is followed by a dispersal of earthy material as dust and the shattering of rock mate- rial into pebbles and rough fragments. The second way is the spontaneous slipping or subsidence of the upper strata after they have begun to crack because of the withdrawal of the underlying substance or foundation; […] While some remain parallel to the horizontal, others become verti- cal; many make oblique angles with the horizon and not a 76 N. Stensen, in ref. 1 (K&M), p. 628. 77 N. Stensen, in ref. 1 (K&M), p. 637. 78 N. Stensen, in ref. 1 (K&M), p. 656. 79 N. Stensen, in ref. 1 (K&M), p. 634. 80 N. Stensen, in ref. 1 (K&M), p. 660. 81 N. Stensen, in ref. 1 (K&M), p. 640. 82 N. Stensen, in ref. 1 (K&M), p. 633. 83 J. W. Valley et al., in ref. 21. few are twisted into curves because of the tenacity of their material. 84 Whereas Steno described deformation of the exterior of minerals, he did not remark on internal effects; so, for this class of time feature, we look to his insights gained from sedimentary strata and compare these to mod- ern studies of zircon. As seen in the above quote Steno made some highly astute observations, recognizing two styles of deformation of strata and their respective geo- metric and material consequences. Steno was accurately describing the range of mechanical responses to different rates of deformation. He did not depict the first style in the Prodromus; that of violent, or very rapid, deforma- tion but it is likely he was referring to the consequences of volcanic activity. The most extreme strain rate events now known to affect planetary crusts occur at the deep- est levels of tectonic collision zones, and, at the most extreme end of the spectrum, within large meteorite impact craters as illustrated here with terrestrial and lunar zircon (Fig. 4). S4 due to rapid deformation Zircon is one of the minerals most resistant to destruction by impact-related shock metamorphism, yet grains develop long-lasting and unique deforma- tion features.85 Fracturing and crystal distortions occur in microseconds and often under extreme, short-lived temperatures of up to a few thousand degrees Celsius. Disordered mineral glasses, instead of secondary miner- als, can fill crystallographic fractures, a material differ- ence alluded to by Steno: “the main cause of variation by which crystal differs from glass not only in refrac- tion but also in other properties, since, in glass, no parts of the dissolving fluid are present, as they have driven forth by the violence of fire”.86 This deformation style of S4 features has been recognized at the Vredefort crater in South Africa, offsetting S1 growth zoning and S2 sur- face of production (Fig. 4). We see a similar sequence in the features of >4 billion year old lunar zircons, includ- ing those recovered by the U.S. Apollo 17 mission near Steno Crater87 (Fig. 4). In both cases, the zircon lattice 84 N. Stensen, in ref. 1 (K&M), p. 636. 85 D. E. Moser, C. L. Cupelli, I. R. Barker, R. M. Flowers, J. R. Bowman, J. Wooden, J. R. Hart. New zircon shock phenomena and their use for dating and reconstruction of large impact structures revealed by elec- tron nanobeam (EBSD, CL, EDS) and isotopic U-Pb and (U-Th)/He analysis of the Vredefort dome. Can. J. Earth Sci., 2011, 48, p. 117-139. 86 N. Stensen, in ref. 1 (K&M), p. 643. 87 B. Zhang et al., Imbrium Age for Zircons in Apollo 17 South Massif Impact Melt Breccia 73155. JGR Planets, 2019, 124, p. 3205-3218 109Crystalline Stenonian Time Features from Earth and Beyond between fracture sets has been bent by several degrees during shock deformation, a mechanical response in line with Steno’s observation for strata which sometimes respond plastically to be “twisted into curves” because of their “tenacity” (above). S4 tectonic fracturing and mineral-fi lled veins Steno also recognized a style of deformation fea- tures such that some strata crack in a brittle fashion to allow fl uid pathways for new mineral precipitates. An example of this sequence of S4 features superimposed on generations of growth features (S1a , S1b) is illustrated here in one of the oldest known fragments of the Earth; a zircon grain from the Archean Jack Hills quartzite from the Yilgarn craton of Western Australia (Fig. 5a). Th e age, chemistry and microstructure of this grain has been described in detail elsewhere.88 Th e central domain (core) has a U-Pb age of 4.38 billion years — a time when the mass of the Moon had already been separated 88 J. W. Valley et al., in ref. 21. from the proto-Earth and the fi rst water appeared,89 the latter reminiscent of Steno’s fi rst fl uids. Th e fi rst set of growth features (S1a) formed during precipitation from a silica-rich magma in Earth’s early continental crust. At modern, average rates of tectonic drift , it is plau- sible that over the last 4 billion years this core domain has circumnavigated the Earth several times as micro- scopic continental cargo on a number of early crustal domains. Roughly 3.4 billion years ago, the grain expe- rienced chemical resorption and/or mechanical abrasion which removed S2 and produced a discontinuity surface, S3, over which grew a new, metamorphic domain with chemical layering (S1b) discordant to the older core. A tectonic deformation produced S4 fractures, which re- oriented the lattice and its S1a, S1b and S3 features, prior to their being fi lled with a combination of new zircon, quartz, and grains of the rare earth phosphate xeno- time, the latter as young as 0.8 billion years ago90(Fig. 5). Th e mineralogy of the micro-veins, and their younger, intersectional age relationship, are directly in line with Steno’s observations of the deformation, veining and growth of secondary minerals.91 Th e sequence of pro- duction (growth), erosion, deformation, and resump- tion of growth experienced by this early Earth zircon resulted in a geometric arrangement of features that is very similar to that which Steno described for the crus- tal strata of Tuscany, illustrating the scale-invariance of Stenonian geochronology (Fig. 5). S4 Deformation and renewed production sequence at atom- ic scales Stenonian cycles of production and modifi cation can also be seen at the atomic level with electron micros- copy at the length scale of Steno’s then “imperceptible particles”,92 as illustrated here in a 200 million year old igneous Mars rock that came to Earth as a meteorite (NWA 5298) ~11 million years ago93 (Fig. 6). Th e cycle of rapid shock-wave deformation and heating, which such shergottite meteorites generally experience as they are ejected to space following an impact event, leaves a record of mm-scale pockets of melting and glass for- 89 SA Wilde, JW Valley, WH Peck, CM Graham, Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago. Nature, 2001, 409, p. 175-178. 90 Rasmussen B. et al., Metamorphic replacement of mineral inclusions in detrital zircon from Jack Hills, Australia: Implications for the Hadean Earth. Geology, 2011, 39, p. 1143-1146. 91 N. Stensen, in ref. 1 (K&M), pp. 629. 92 N. Stensen, in ref. 1 (K&M), pp. 626. 93 Moser, D. E. et al., Solving the Martian meteorite age conundrum using micro-baddeleyite and launch-generated zircon. Nature, 2013, 499, p. 454-457. Figure 4. Examples of violent deformation features (S4 ) on Earth and the Moon: a) a boulder of Archean (~3 billion year old) crust near the center of the ~250 km wide, 2.020 billion year old Vrede- fort impact structure of South Africa. b): SEM-CL image of a zir- con crystal from this region c) boulder at the edge of Steno Crater ( Apollo 17), d) SEM-CL image of a >4 billion year old zircon from near site shown in c). 110 Desmond E. Moser mation as well as a suite of microscopic S4 deformation features within the regular atomic layering of igneous crystals. Th e heating also triggers short-lived chemi- cal reactions and local growth of minerals, including zircon, during cooling en route to space.94 Th e result- ing continuous and discontinuous patterns among the atomic lattice layers, revealed with electron microscopy, are analogous to the those in strata in Steno’s sketches of Tuscan geology (Fig. 6). We can see in Figure 6 that primary atomic layering (S1a) in the Mars mineral badde- leyite (ZrO2), has been re-oriented and disordered across S4 surfaces of deformation. A boundary of chemical reaction (S3) separates the deformed baddeleyite features from younger, atomic layers of undeformed zircon (S1b) at the start of its journey to Earth (Fig 6). Th is atom- scale Stenonian geochronology, when paired with abso- lute geochronology methods, allows for back-stripping 94 ibid. and dating of a microscopic deformation and chemical erosion sequence developed on a path between planets.95 f ) S5 Chemical dif fusion, chronostructures, and Steno’s known unknown process Th us I do not determine whether particles of a natural substance can or cannot undergo change, as its shape can, whether there are or are not minute empty spaces whether in those particles, in addition to the ability to occupy space and the property of hardness, there may not be something else unknown to us; for these statements are not widely accepted, and it is a feeble argument to deny that there is anything else in a certain thing because I do not observe anything else in it. 96 95 ibid. 96 N. Stensen, in ref. 1 (K&M), p. 626. Figure 5. Cyclic growth and deformation; a) Steno’s depiction of Tuscan strata (see text for description of annotations), b) SEM -CL image of one of Earth’s oldest known mineral grains, zircon with a 4.38 billion year old core. Th e 3.6 billion year sequence of growth, erosion, deformation and renewed growth features can be seen in higher magnifi cation view of white dotted box, enlarged in c). 111Crystalline Stenonian Time Features from Earth and Beyond Th e fi ft h class of time features are surfaces of chem- ical discontinuity created by atomic movements and are distinct from the other four classes in terms of both the strength of connection to Steno and the source of their geometric form. Unlike the other feature classes, Steno did not specifi cally predict structures at the atomic scale in nature as this was out of observational range. Yet, as can be seen above, he allowed for their existence. Th ey are included here as Stenonian features because Steno’s writings in both the Prodromus and his later Prooemi- um on the topic of particle (atomic) motion and heat have been previously interpreted as descriptions of dif- fusion.97 Th is feature class diff ers also in regard to form in that S5 is not a single, discrete surface but a pair of subparallel surfaces bounding a gradient of chemical 97 J. M. Hansen in ref. 33. change caused by a migration of atoms aft er solid for- mation. Steno held the Cartesian view that “A natural body is an aggregate of imperceptible particles”,98 and with recent advances in microscopy, geochronologists can now image and measure the three dimensional dis- tribution of these particles, as either or both elements and isotopes, within minerals.99 Of particular inter- est in zircon are the isotopes 206Pb and 207Pb which are the stable decay products of 238U and 235U, respectively. It has recently been found that exposure of zircon to extreme heat in the Earth or in impact craters can cause Pb isotopes to migrate (diff use) and pile up within the zircon lattice, thereby forming structures sensu stricto (Fig. 7). I here introduce the term ‘chronostructure’ for 98 N. Stensen, in ref. 1 (K&M), p. 626. 99 J. W. Valley et al., in ref. 21. Figure 6. Stenonian time features at atomic scale in a meteorite from Mars; a) a view of Mars strata, Opportunity Rover; b) a STEM image of the shock-deformed atomic layers in baddeleyite (S1a) reacting to undeformed zircon (S1b) in Mars meteorite NWA 5298; Higher magnifi - cation STEM images of the disturbed baddeleyite lattice (c), and undeformed zircon lattice (d). e) Steno’s Diagram 22. 112 Desmond E. Moser this type of S5 feature as it is a concentration of atoms assembled during an event; an outcome of the universal process of elemental diffusion within or between miner- als assisted by either or both deformation and tempera- ture.100 Zircon presents a special case in that its lattice contains no Pb at the time of zircon crystallization due to energetic exclusion. Thus, each Pb atom seen today is radiogenic and itself an expression of geologic time. Zir- con Pb chronostructures reported so far have a variety of shapes but seem to be mostly spheroidal. Examples have been documented from several regions on Earth and the Moon.101 One example can be seen in a zircon from near the centre of the Vredefort structure in South Africa where, one billion years after its formation, the largest recognized terrestrial impact event caused its S1 growth zoning to be cross-cut by S4 shock deforma- tion features (Fig. 7). These contain nanodomains of Pb enriched ~1000x above background levels due to impact-related heating and diffusion. Such chronostruc- tures represent a new type of feature in absolute geo- chronology. 100 E. B. Watson, E. F. Baxter, Diffusion in solid-earth Systems. Earth and Planetary Science Letters, 2007, 253, p. 307-327. 101 See list of citations in G. A. Arcuri et al., in ref. 40. 4. DISCUSSION This reconsideration of Steno’s time features in minerals in comparison to those for other solids brings to light several themes that illuminate Steno’s past and continuing contributions to mineralogy and geochro- nology. One is his perhaps revolutionary perception of scale invariance among the processes of solid formation in nature; an advance that is implicit in the Prodromus but not always recognized. A second theme relates to the source of his observational acuity and the provenance of his scientific philosophy which, together, enabled him to recognize geologic history. Finally, the consistent agree- ment between Stenonian geochronology with modern microscopy and zircon geochronology opens the door to considering Steno’s large, and largely unrecognized, importance in the practice of absolute geochronology. Steno’s fractal features What I demonstrate about Tuscany by induction from many places examined by me, so I confirm for the whole earth from the descriptions of many places set down by various writers.102 It is apparent from Steno’s geochronology observa- tions (Table 1) that he saw his results as transcending geography and spatial scale. Steno clearly believed that his findings would have global application, perhaps fol- lowing the globalist thinking of Descartes which had so impressed him103. His view of local processes as a subset of universal operations of the Earth can also be seen as in line with the long philosophic history of macrocosms and microcosms which saw the human body as a facsim- ile of the workings of an animate Earth.104 Certainly our examples from zircon geochronology show that Stenon- ian features are applicable to samples from the Earth and beyond, representing stages in most of the solar system’s history. Steno’s implicit awareness of the frac- tal and scale-invariant properties of the visual records in solids, in regard to both space and time, has not been amplified in previous studies of his work, in general, and in mineralogy, in particular. His freedom of mind in respect to physical scale is illustrated in his plate of diagrams105 wherein he juxtaposes cross sections of cm- scale crystals with two dimensional profiles through a mountainous landscape. Although cross-sectional views 102 N. Stensen, in ref. 1 (K&M), p. 654. 103 D. Garber, in ref. 29. 104 G. P. Conger, Theories of macrocosms and microcosms in the history of philosophy. New York, Columbia University Press, 1922, 142 pp. 105 N. Stensen, in ref. 1 (K&M), p. 658. Figure 7. Example of a feature resulting from atomic diffusion (a ‘chronostructure’), related to Steno’s allusion to such phenomena: Left) A SEM-CL image of a shock -metamorphosed zircon from the Vredefort impact crater zircon, Right) perspective view of a three dimensional atom map of Pb (concentrated above 2%, green sur- face) and U isotopes imaged in a microscopic needle sampled from this grain (arrow). 113Crystalline Stenonian Time Features from Earth and Beyond of the Earth were not uncommon in the 17th century,106 Steno’s clear, connection of mineral and land evolution appears to have been without precedent in European natural philosophy. A metaphor for Steno’s awareness of fractal scale invariance appears in his earlier writings when praising the scope of the human mind enabled by the Creator: “Finally he will penetrate the inside of the earth and discover the hidden mysteries of the minerals. All these representations respond to a sign as if the mac- rocosmos laid hidden in the microcosmos”.107 This accu- rate, fractal vision points to Steno’s special abilities and method for natural philosophy. Steno’s methodologic innovation It is proposed that Steno’s achievements in the Pro- dromus were made possible by his innovative pairing of an innate, finely-tuned awareness of the process of visual observation and cognition with a set of Stoic ethical pre- cepts gained earlier in his career, all coming to fruition on the Galilean soils of Florence. Unless the mind is tranquil, it will by no means be free to apply itself to a close examination of facts which can and ought to be closely examined, and unless every least detail is noted in so far as the minuteness of the object or its intri- cate diversity allows, the pathway to error is downhill and very easy.108 The quality underpinning the classes of scale-invar- iant time features (Table 1) is that of the cognition of continuity of visual elements in regard to either chem- istry or geometric orientation; but, how do we sense continuity? Neuroscience has recently shown that our visual sensory system operates with an inherent “con- tinuity field” such that we have a short-term percep- tual bias toward continuity of orientation in geometric forms.109 The timespan of the continuity field’s influence on human perception was measured at ~15 seconds; operating only near the observer’s point of focus. It fol- lows that accurate visual cognition of patterns in nature requires time to overcome this natural bias. There is evidence that Steno was very aware from his anatomi- cal training and research that focused, prolonged visual inspection was requisite for accurate science (above). Moreover, he recognized the reward of careful observa- tion in teaching and advancing science in his own time: 106 T. Yamada, in ref. 33. 107 N. Stensen, in ref. 1 (K&M), p. 74. 108 N. Stensen, in ref. 1 (K&M), p. 112. 109 J. Fischer, D. Whitney, Serial dependence in visual perception. Nature Neuroscience, 2014, 17, p. 38-743. “Sometimes it takes years to discover that which can then be demonstrated to others in less than an hour”.110 Philosophers who presaged the work of Linnaeus in the next century concentrated on “the external (and particu- larly the visible) structures of natural objects” 111 and, as mentioned above, Steno’s examination of the inter- nal zones of crystals was, in this regard, an innovation. Moreover, upon his arrival in Florence, Steno immedi- ately engaged with the members of the Accademia del Cimento which followed in the ‘anti-scholastic’ Gali- lean scientific tradition of experimentation and observa- tion, and responded by taking the middle way between scholastics and experimentalists.112 His primary instru- ment was human vision with which he interpreted, or abducted,113 in the language of geo-semiotics,114 meaning from the landscape. It is proposed that Steno’s awareness of the need for self-discipline and time spent in obser- vation was also guided by an awareness of the quali- ties of observation required if his deductions were to be deemed accurate and recognizable to others. I decided to press with all my might in physics for what Seneca often urges strongly regarding moral precepts; he states that the best moral precepts are those which are in common use, widely accepted, and which are jointly pro- claimed by all from every school.115 Perhaps one of Steno’s strongest innovations in methodolog y was to integrate the Galilean experi- mentalist tradition of Florence with elements of Stoic philosophy as expressed by Seneca (above). Stoic phi- losophy was respected by the humanists for its system- atic approach, and it is perhaps unsurprising to see it appear in Steno’s work given his time as a student in Leiden, which is considered to have been the heart of Neo-Stoicism in 16th and 17th century Europe,116 and where Steno sought out the rich diversity of intellectual thought of the Dutch Golden Century.117 Steno applies the Stoic (Senecan) tradition in ethics of considering only those sensations all can agree on, and falling with- in the area of intersection of all scholars’ perceptions. Steno’s adoption of this aspect of Stoicism to his treat- 110 N. Stensen, in ref. 1 (K&M), pp. 128. 111 W. R. Albury, D. R. Oldroyd, in ref. 27. 112 J. Bek-Thomsen, in ref. 8. 113 J. E. H. Smith, Thinking from traces. Nicolas Steno’s palaeontology and the method of science, in ref. 8, p. 177-200. 114 V. R. Baker, Geosemiosis. GSA Bulletin, 1999, 111, p. 633–645. 115 N. Stensen, in ref. 1 (K&M), p. 626. 116 J. Lagrée, Justus Lipsius and neostoicism, in The Routledge handbook of the Stoic tradition (Ed. J. Sellars), Taylor & Francis Group. 117 E. Jorink, Modus politicus vivendi. Nicolaus Steno and the Dutch (Swammerdam, Spinoza and Other Friends), 1660–1664, in ref. 8, p. 13-44. 114 Desmond E. Moser ment of the results of his visual, Galilean experiments in the field allowed him to distill and communicate his uniquely systematic interpretation of natural history. Steno and modern geochronology To recognize the temporal in the spatial – nobody had done that before Stensen –, from the whole rock to read a dynamic course of time, has since then become and remained the main object of scientific geology.118 It can be argued that Galilean science, and the Pro- dromus, are similarly rooted in the sensation and meas- urement of time. In 1654, Viviani reported that a youth- ful Galileo used the period of his heartbeat to recognize the isochronous swings of a lantern through the space beneath the Duomo of Pisa,119 leading, ultimately, to his famous pendulum studies of the strength and ori- entations of gravity. One might sense echoes of this approach in the Prodromus in which Steno recognized the geometric tracings of time in solids using his highly attuned perception of discontinuity and its, embedded component of time. Steno extended his extraordinary pattern recognition, likely refined through his years of anatomical research, to further place an order on sets of visible features, as in his reconstruction of Tuscan geol- ogy; “obvious inequalities in the present surface contain within themselves clear indications of various changes, which I shall review in inverse order, working back from the most recent to the first”.120 In both strata and miner- als (e.g. Fig. 1), Steno was thus the first to so methodical- ly order past geologic events based on field experiments, setting the relative geochronology framework which would be employed by Holmes in his proof-of-concept of absolute geochronology more than two centuries lat- er. Stenonian method continues to be vital in geochro- nology as technical advances enable sampling of ever- smaller volumes and atom-scale observation of elements, isotopes and chronostructures becomes more widely applied; for it is axiomatic that absolute geochronology is dependent on the length-scale of sampling owing to Holmes’ principle of the closed chemical system. Con- versely, Steno’s spatial system of relative geochronol- ogy is scale-invariant in respect of both space and time. Steno’s classes of visible features of production and mod- ification therefore continue to serve as an independent, intensive, time measurement system for interpreting and checking the accuracy of absolute, extensive, geochro- 118 K. von Bülow, in ref. 5. 119 S. Gattei, On the life of Galileo: Viviani’s historical account and other early biographies. Princeton University Press, 2019, p. 440. 120 N. Stensen, in ref. 1 (K&M), pp. 653. nology age measurements to allow us to achieve a more accurate geochronology. 5. CONCLUSION Steno’s Prodromus has been recognized by many scholars as a brilliant, though loosely organized, advance in human observation and perception of records of geo- logic time in solids. A reconsideration and classification of Steno’s writings on processes deduced from solids, and especially atomistic processes in mineral bodies, in terms of visual time features brings to light addi- tional Stenonian advances. Successful comparison of Steno’s time features with electron microscopy down to atom scale help demonstrate Steno’s implicit appre- ciation of the fractal, scale-invariant nature of time fea- tures. Steno’s methodologic advances are also discussed; with the proposal that it was Steno’s combination of his awareness of the precision and accuracy of the human visual system with Stoic, and particularly Senecan, pre- cepts in ethics which propelled his remarkable achieve- ments in the rich, Galilean scientific environment of Florence. Finally, it is argued that the intensive quality of Stenonian geochronology causes it to be an invaluable check on the accuracy of extensive, absolute geochrono- logic age values, thus asserting the modernity of Steno in the geochronology of solids from Earth and beyond. ACKNOWLEDGEMENT I gratefully acknowledge helpful reviews of ear- lier versions of this manuscript by Yuri Amelin and Jens Morten Hansen. Many thanks to Eric Jorink for his review and helpful directions to Stoic literature. Nuno Castel-Branco is thanked for assistance accessing Steno literature early in the pandemic. Gabriel Arcuri is thanked for assistance with Figure 7. The author gratefully acknowledges his many collaborators associ- ated with the microscopy presented here. Helpful edi- torial comments by G. D. Rosenberg are very gratefully acknowledged. Stefano Dominici is especially thanked for patient and supportive reviews and guidance, impor- tant Steno references, and direction in navigating histor- ical science literature and conventions. NASA Apollo 17 astronauts and mission scientists are sincerely thanked for lunar photograph in Fig 5. NASA/JPL/Cornell are acknowledged for the Burns Cliff, Endurance Crater, Opportunity Rover image in Fig. 6. Participants in the Oct. 2019 symposium at the University of Florence are thanked for many conversations and generous sharing of their wealth of Steno knowledge.