A first and last outpost for life on Mars? Insights from ancient hot springs in the Pilbara

Transcription

1 A first and last outpost for life on Mars? Insights from ancient hot springs in the Pilbara What can studying early life on Earth tell us about origins of life? How can this shape our search for life elsewhere? T.Djokic, M. J. Van Kranendonk, M. R. Walter, K. A. Campbell, D. Deamer, B. Damer

2 Historical perspectives 1871 Charles Darwin My dear Hooker, if (and oh what a big if) we could conceive in some warm little pond with all sorts of ammonia and phosphoric salts, light, heat, electricity & c. present, that a protein compound was chemically formed, ready to undergo still more complex changes.. Chemical factories/diverse life

3 Historical perspectives Late 20 th century, deep seafloor hot vent discoveries Which are also chemical factories/diverse life Since their discovery, much of origin of life literature (until recently) has focused on these sites

4 Early Earth considerations Hydrothermal vents in the ancient rock record known for some time (Vearncombe, 1995) Very little land surface on the early Earth Global ocean High heat flux, lots of volcanism = deep sea hydrothermal vents abundant on early Earth = good candidate for origin of life model Our recent work in the Pilbara provides an alternative perspective..

5 The 3.5 billion year old Dresser Formation Type of life? Type of environments? The Pilbara, Western Australia

6 Some of the oldest evidence for life on Earth Earth is ~4.6 billion years old These rocks are ~3.5 billion years old Older evidence ~4 billion years old highly contentious in comparison Life first discovered in the late 1970 s.. Stromatolites Rock structures built by Communities of micro-organisms How do we know this?

7 Stromatolites still live today Fossil stromatolites Modern stromatolites, Shark Bay Stromatolite fossils Complex life 4.6 billion y.a 500 million y.a present

8 3.5 billion year old Dresser Formation, WA Original research in the 1980s. Similar dome shaped stromatolites Modern stromatolites, Shark Bay

9 Geysir, Iceland Subsequent research 2000 and beyond Extend record of life in hot springs by 3 billion years - Oldest hot springs prior to this work was from 400 million year old deposits Shark Bay, Western Australia But, what was missing from this environmental model An ancient volcano, e.g. White Island, NZ - Oldest evidence for life on land was from 2.7 billion year old deposits 2017 Key evidence: Geyserite With life. - Contrary to previous evidence, life thrived on land very early on!

10 Early Earth considerations Evidence Hydrothermal for ~3.5 vents billion in the year ancient old hot rock springs record on known land for (Djokic some et time al., Nat. (Vearncombe, Comm. 2017) 1995) Very Land land as early surface as on 4.4 the billion early years Earth ago (Wilde et al., 2001; Valley et al., 2014) Global ocean High heat flux = deep sea hydrothermal vents abundant on early Earth = good candidate for origin of life model = From a geological perspective, Darwin s warm little pond a contender

11 Origin of life arguments: a close up Hydrothermal vents on the ocean floor Hot springs at the surface *Sharp chemical and temp gradients *Plenty of microbial life Submarine - Rock-water interaction - Diluted environment Why is this important in the search for life elsewhere? *Sharp chemical and temp gradients *Plenty of microbial life Land based - Air-water, air-rock, rock-water interaction - Wet/dry cycles - Allows complex molecules > needed to make life (Deamer & Damer)

12 Considerations for the search for life elsewhere Hypothetically, if life started on land and not in the deep oceans, the implications for the search for life could be constrained.. Enceladus Actual size Habitable, yes. Ever inhabited?? Europa Mars Habitable, yes. Ever inhabited? Maybe?

13 Mars2020 Of the top 3 chosen landing sites, one is a ancient hot spring About the same age as the early Earth ~3-4 billion years old Other two environments interpreted through remote data NE Syrtis Major: Various ancient aqueous environments (Carbonate rocks/deep aquifers) Jezero Crater: Ancient lake Delta Columbia Hills: Ancient volcanic and hot spring environment - Only one visited by rover, Spirit

14 Columbia Hills Hot springs observed by Spirit Rover Operated ( ) before wheel jammed But not before

15 Images sent back by Spirit Digitate structures made of silica Mars El Tatio, Chile, Earth Fossilized bacteria Article; Ruff et al., Nat. Comm.

16 What we know Biochemical studies point to land based hot springs as a site for the origin of life We now know hot springs were inhabited very early on in Earths history We know Earth and Mars were once quiet similar both having liquid water on the surface and volcanic activity Even though their planetary evolution diverged, 3.5 Billion years ago?? there is evidence for ancient hot springs on Mars that resemble hot springs with fossilised microbes on Earth?? Now Columbia Hills ~3.5 billion year old stromatolite are preserved in ancient hot springs on Earth Mars Earth

17 Thank you