The Role of Meteorite Impacts in the Origin of Life

Abstract

The conditions, timing, and setting for the origin of life on Earth and whether life exists elsewhere in our solar system and beyond represent some of the most fundamental scientific questions of our time. Although the bombardment of planets and satellites by asteroids and comets has long been viewed as a destructive process that would have presented a barrier to the emergence of life and frustrated or extinguished life, we provide a comprehensive synthesis of data and observations on the beneficial role of impacts in a wide range of prebiotic and biological processes. In the context of previously proposed environments for the origin of life on Earth, we discuss how meteorite impacts can generate both subaerial and submarine hydrothermal vents, abundant hydrothermal-sedimentary settings, and impact analogues for volcanic pumice rafts and splash pools. Impact events can also deliver and/or generate many of the necessary chemical ingredients for life and catalytic substrates such as clays as well. The role that impact cratering plays in fracturing planetary crusts and its effects on deep subsurface habitats for life are also discussed. In summary, we propose that meteorite impact events are a fundamental geobiological process in planetary evolution that played an important role in the origin of life on Earth. We conclude with the recommendation that impact craters should be considered prime sites in the search for evidence of past life on Mars. Furthermore, unlike other geological processes such as volcanism or plate tectonics, impact cratering is ubiquitous on planetary bodies throughout the Universe and is independent of size, composition, and distance from the host star. Impact events thus provide a mechanism with the potential to generate habitable planets, moons, and asteroids throughout the Solar System and beyond.

Keywords: Crater lakes; Geobiology; Hadean environment; Hydrothermal systems; Impact craters; Lithophytic habitats; Origin of life.

FIG. 1.

Images of impact craters showing the change in morphology with increasing size. (A) The 3 km diameter Zumba Crater on Mars, a prototypical simple crater. Note the impact ejecta deposits (“e”) and the impact melt deposits (“m”) on the crater floor. Portion of Mars Reconnaissance Orbiter High Resolution Imaging Science Experiment (HiRISE) image PSP_003608_1510. NASA/JPL/University of Arizona. (B) The 93 km diameter Pettit Crater on Mars, a well-preserved complex crater with a central peak (“cp”). THEMIS day-time mosaic. NASA/JPL/Arizona State University. (C) With increasing diameter, central peaks are replaced by peak-rings (“pr”) as in the case of the ∼320 km diameter Schrödinger Crater on the Moon. The crater has well-preserved ejecta deposits, and impact melt occurs both inside and outside the peak-ring. Lunar Reconnaissance Orbiter (LRO) Wide Angle Camera (WAC) mosaic. NASA/JPL/ASU. (D) The largest impact features in the Solar System are termed impact basins, such as the ∼900 km diameter Orientale Basin on the Moon shown here. It contains three ring features labeled 1–3. LRO WAC mosaic. NASA/JPL/ASU.

FIG. 2.

Variation in pressures and temperatures from the thermobaric to equilibrium phase of crater formation and the major substrates and habitats associated and utilized during each stage. Note that a habitat or substrate may remain used during subsequent stages (e.g., porous rocks and glasses can remain important habitats during the equilibrium phase). The temperature curves represent an average and will be different for different parts of a crater (see text for details).

FIG. 3.

Backscattered electron images showing the progressive physical changes in crystalline rocks from the Haughton impact structure with increasing shock pressure. (A) Unshocked gneiss with essentially no porosity and few fractures. (B) In Shock Level 2 samples (∼5–10 GPa), all minerals are fractured to varying degrees. Average porosity is ∼1%. (C) Shock Level 3 (∼10–30 GPa). All minerals are heavily fractured with planar deformation features in quartz and average porosities of ∼2–5%. (D) In Shock Level 5 (∼35–55 GPa) samples there is extensive development of diaplectic glass in quartz. Feldspar has undergone melting to form vesiculated glass. Average porosities are ∼18%. (E) Shock Level 6 (∼55–60 GPa). All minerals are transformed to diaplectic glass or partially to completely melted and transformed to mineral glasses. Average porosities are ∼44% (F) In Shock Level 7 (>60 GPa) samples, all minerals have melted and transformed to glass. Average porosities are ∼63%. All scale bars are 100 μm. Abbreviations: qtz = quartz; feld = feldspar; cpx = clinopyroxene; gl = glass. The black regions in all images are holes in the thin sections. Porosity values are from Pontefract et al. (2014).

FIG. 4.

Artistic rendition of a typical complex impact crater at end of thermobaric phase. At this time, the hydrosphere remains severely disrupted, and the crater interior is filled with impact melt deposits that are superheated to temperatures over 2300°C. Ponds and flows of hot impact melt also occur in patches on top of the ballistic impact ejecta deposits in the crater exterior. The target rocks inside the crater are heavily fractured and shock metamorphosed with shock pressures increasing toward the center.

FIG. 5.

Artistic rendition of a typical complex impact crater during the hydrothermal phase. If conditions permit, a hydrothermal system and crater lake can develop, along with several other habitats (described in Section 4).

FIG. 6.

(A) Distribution of the six major settings for impact-generated hydrothermal alteration deposits within and around a typical complex impact crater (modified from Osinski et al., 2013). (B) Quartz vug in crater-fill impact melt rocks, West Clearwater Lake impact structure, Canada. (C) Hydrothermal pipe structure interpreted as fossil hydrothermal vent in the rim region of the Haughton impact structure. (D) Altered impact melt-bearing breccia from the Ries impact structure, Germany. (E) Clay lining a vesicle within impact melt-bearing breccia from the Chicxulub impact structure, Mexico. (F) Zeolite within impact melt-bearing breccia from the Chicxulub impact structure, Mexico. (G) Calcite vein in the central uplift of the Haughton impact structure, Canada.

FIG. 7.

Endolithic lithophytic habitats in impactite lithologies. (A) Increased porosity in a shocked gneiss from the Haughton impact structure provides a physical habitat for a continuous band of cyanobacteria ∼2–5 mm below the rock surface (Cockell et al., 2002). (B) Confocal laser scanning micrograph showing live (green) and dead (red) microorganisms colonizing void spaces in a shocked gneiss from the Haughton impact structure (modified from Pontefract et al., 2014). (C) Backscattered electron microscope image of osmium-stained cyanobacteria and thylakoid membranes (white) colonizing a shocked gneiss from the Haughton structure. (D) Impact glass from the Ries impact structure provides a substrate for euendoliths (modified from Sapers et al., 2015).

FIG. 8.

Impact crater lake environments and habitats. (A) The 3.44 km diameter New Quebec or Pinguluit Crater is a well-preserved simple impact crater in northern Quebec, Canada. The crater lake is ∼270 m deep and has no inlets or apparent outlets. (B) The West (“W”) and East (“E”) Clearwater Lake impact structures in Quebec are ∼36 and ∼26 km in diameter, respectively, and both contain crater lakes. (C) Hydrothermally altered coarse-grained sediments deposited at the base of the Ries crater lake. The orange color is due to hydrothermal iron oxides and clays. Sample is from 14.3 m depth in the Wörnitzostheim drill core. (D) Alteration halo around a calcite-lined cavity in fine-grained lake sediments in the Nördlingen drill core (323 m depth), Ries impact structure. (E) Stromatolitic limestone from the upper part of the Ries crater lake succession. Finger for scale.