David Catling

Professor, Univ of Washington @UW , Planetary Sciences, Astrobiology, Origin of Life,

[David Catling @DavidCCatling]

published a paper that melts little balls of iron in the lab to mimic how micrometeorites melt in the upper atmosphere. New kinetic data helps us use micrometeorites in rocks from billions of years ago to find the composition of ancient air at that time. https://t.co/85niynv07Q

[David Catling @DavidCCatling]

Earth was a frozen over, "Snowball Earth" twice, between 720-635 m.y. ago. The 1st one lasted a huge 56 m.y. (almost like dinosaur extinction to us) but no one knows how. My group just published a mechanistic explanation. https://t.co/cLSy8Abn9z

[David Catling @DavidCCatling]

New co-authored paper with my former student, Nick Wogan. A physics-chemistry code that can simulate the atmospheres and climates of Venus, Earth, Mars, Jupiter, and Titan. Will be useful for interpreting exoplanet spectra. https://t.co/rgSxeA0vb7

[David Catling @DavidCCatling]

what I'm reading: a phosphorus story. Opens, "There would be no life without constant death". Ch. 1 tells how Darwin's mentor, John Henslow, realized in 1842 that rocks could supply P fertilizer. The first mine, 1847, was where Henslow found phosphate-rich rocks: Felixstowe, UK.

[David Catling @DavidCCatling]

glad that my book, “Astrobiology: A Very Short Introduction” (1st Ed with updates, Yilin Press, Nanjing) is now published in Chinese and available to the 1.2B people for whom Chinese is a first or second language.

[David Catling @DavidCCatling]

@SFurkanOzturk61 Elemental sulfur can also be formed in a reducing atmosphere from photolysis of SO2 and subsequent photochemistry. But then it would be globally dispersed so I would guess the fumarolic or crater lake source for the martian stuff.

[David Catling @DavidCCatling]

happy to have contributed to a Perseverance Rover crystallographic study of sulfates on Mars, showing how some formed in near-surface fluids & others deeper. https://t.co/WS4tIW61EG

[David Catling @DavidCCatling]

@SFurkanOzturk61 Terrestrial example: https://t.co/8DRaNJ0kvJ

[David Catling @DavidCCatling]

@SFurkanOzturk61 2/2: How? Cooling & reaction of magmatic gases: 2H2S + SO2 = 3S + 2H2O;
disproportionation-hydrolysis of SO2 can also make S: 3SO2 + H2O = 2SO4(2-) + H2O + S + 4H+;
oxidation of H2S to thiosulfate, and its breakdown:
2H2S + 2O2 = S2O3(2-) + H2O + 2H+ ; S2O3(2-) = S + SO3(2-)

[David Catling @DavidCCatling]

@SFurkanOzturk61 On Earth, elemental sulfur is found in fumaroles or geothermal / hyper-acid crater lakes. 1/2

[David Catling @DavidCCatling]

Methane can be biotic so is of interest on Mars. There, the Trace Gas Orbiter finds no CH4 but Curiosity Rover detects CH4. A discrepancy. We show that the latter is plausibly internal contamination, however. https://t.co/t1lgdijTlI

[David Catling @DavidCCatling]

Research by colleagues & me covered in Science magazine this week https://t.co/5Rq9D20f5P

[David Catling @DavidCCatling]

@KellyDobitz @uwastrobiology Some microbes have made this journey. E.g., most work favors a freshwater origin for cyanobacteria (e.g., phylogenetics by Sanchez-Baracaldo). By number, they're now extremely abundant in the ocean. 2/2

[David Catling @DavidCCatling]

New paper: We quantified phosphorus fluxes in soda lakes, showing that without biology, soda lakes worldwide would have phosphate levels suitable for prebiotic synthesis, answering the 70-year-old “phosphate problem of the origin of life" @uwastrobiology
https://t.co/WHmqzTfrMV

[David Catling @DavidCCatling]

@KellyDobitz @uwastrobiology Changes in hydrology / geology can also connect lakes to the sea. E.g., some soda lakes are on ocean islands. Such islands sink over time and reach sea-level. 1/2

[David Catling @DavidCCatling]

@grahbudd Very sorry to hear that. He invited me to Stockholm once & was very kind during my visit.

[David Catling @DavidCCatling]

“Timing and Likelihood of the Origin of Life Derived from Post-Impact Highly Reducing Atmospheres” from my group. We calc. that life began in the Hadean with median estimate ~4.35 Ga. Consistent with recent @glpcjd phylogenetic inference of LUCA ~4.2 Ga. https://t.co/4tlmCBQJEZ

[David Catling @DavidCCatling]

What I’m reading. I like the coverage of the origin of life in this book, amongst other things.

[David Catling @DavidCCatling]

Concretions are hard mineral accumulations of different composition from surrounding rock, deposited from dissolved minerals in subsurface water. Part of team reporting them from NASA’s Mars Perseverance Rover today. https://t.co/gFwVvakEsA

[David Catling @DavidCCatling]

What happened after most of the Earth froze over between 645-635 million years ago, the last “Snowball Earth”? Published today:

Trent B. Thomas & David C. Catling, Nature Communications https://t.co/AmzIIdZylm