Sébastien Viscardy

www.youtube.com/watch?v=AG0H...

31.07.2025 21:39 — 👍 0    🔁 0    💬 0    📌 0

Schematics of atmospheric CH4 cycling on (a) modern Earth, (b) Archean Earth, and (c) Titan. (a) On modern Earth (20% O2), CH4 emissions originate primarily from wetlands, ruminants, and the fossil fuel industry. Methane is oxidized chemically in the troposphere by hydroxyl radicals (OH), with an average lifetime of 10 years. Hydroxyl radicals originate from reactions between ozone (O3), UV radiation (<320 nm), and H2O vapor. The O3 layer originates from reactions between UV radiation and O2. (b) On the Archean Earth (<0.0001% O2), in the absence of O3 and O2, CH4 would have had a much longer atmospheric lifetime (∼10,000 years), with eventual destruction by UV photolysis, leading to H escape and/or, when CH4/CO2 was greater than 0.1, polymerization to yield organic haze in the upper atmosphere. (c) On Titan, with temperatures near the CH4 triple point, there is a CH4 cycle of evaporation, photolysis to yield ethane (C2H6) and H2 (lost to space), and condensation of C2H6, whereupon it participates in surface processes.

Review of methane through space and time, coauthored with @planetdr.bsky.social, is out (OA) in @annualreviews.bsky.social.

Hopefully a helpful resource for community and courses. www.annualreviews.org/content/jour...

02.06.2025 13:17 — 👍 50    🔁 20    💬 1    📌 3

Proposed Experiment Could Clarify Origin of Martian Methane - Eos Curiosity’s detection of the gas, if atmospheric, could be an indicator of life on the Red Planet. But skeptics say further work is needed to rule out the rover itself as the source of the methane.

Great news! Our paper questioning the methane detections on Mars by Curiosity has been featured as an Eos Research Spotlight:

eos.org/research-spo...

12.05.2025 14:37 — 👍 1    🔁 0    💬 0    📌 0

Embark on a thesis with us from the start of the 2025-2025 academic year to decipher the composition of comet 67P!
#PhD #astrochemistry #astrobiology

@upecofficiel.bsky.social @ipsl.bsky.social @lisa-ipsl.bsky.social

02.05.2025 11:45 — 👍 4    🔁 4    💬 1    📌 1

This recital by Grigory Sokolov is definitely one of the best performances of Rachmaninov’s Opus 23 Preludes.

www.youtube.com/watch?v=awcs...

28.04.2025 16:41 — 👍 0    🔁 0    💬 0    📌 0

Questioning the Reliability of Methane Detections on Mars by the Curiosity Rover Methane levels in Curiosity's Tunable Laser Spectrometer foreoptics chamber are 3–4 orders of magnitude higher than in the sample cell Using a diffusion model, we propose a leakage scenario from ...

Bonjour Hervé,

Voici un nouvel article, réalisé en collaboration avec David C. Catling et Kevin Zahnle, dans lequel nous remettons en question les détections de méthane prétendument martien obtenues par Curiosity.

doi.org/10.1029/2024...

28.04.2025 07:32 — 👍 0    🔁 0    💬 1    📌 0

Questioning the Reliability of Methane Detections on Mars by the Curiosity Rover Methane levels in Curiosity's Tunable Laser Spectrometer foreoptics chamber are 3–4 orders of magnitude higher than in the sample cell Using a diffusion model, we propose a leakage scenario from ...

The mystery of Mars methane 🤔
Before phosphine on Venus and DMS on K2-18b, methane on Mars was the hottest biosignature around, and a major result for Curiosity.
Problem is, I've been searching for it with ExoMars for seven years and haven't seen a trace.....🧵
#planetsci 🧪🔭
doi.org/10.1029/2024...

26.04.2025 18:01 — 👍 59    🔁 13    💬 1    📌 2

Questioning the Reliability of Methane Detections on Mars by the Curiosity Rover Methane levels in Curiosity's Tunable Laser Spectrometer foreoptics chamber are 3–4 orders of magnitude higher than in the sample cell Using a diffusion model, we propose a leakage scenario from ...

Impressive detective work.

It’s possible that previous reports of detection of methane on Mars are contamination.

Will await results from rover after conducting the suggested tests.

agupubs.onlinelibrary.wiley.com/doi/10.1029/...

13.04.2025 20:37 — 👍 13    🔁 5    💬 1    📌 0