Reports of methane in the martian atmosphere have been intensely debated because detections have been very sporadic in time and location, and often fell at the limit of the instruments' detection limits. ESA's Mars Express contributed one of the first measurements from orbit in 2004, at that time indicating the presence of methane amounting to 10 ppbv.
Earth-based telescopes have also reported both non-detections and transient measurements up to about 45 ppbv, while NASA's Curiosity rover, exploring Gale Crater since 2012, has suggested a background level of methane that varies with the seasons between about 0.2 and 0.7 ppbv – with some higher level spikes. More recently, Mars Express observed a methane spike one day after one of Curiosity's highest-level readings.
The new results from TGO[*] provide the most detailed global analysis yet, finding an upper limit of 0.05 ppbv, that is, 10–100 times less methane than all previous reported detections. The most precise detection limit of 0.012 ppbv was achieved at 3 km altitude.
[*] TGO: ExoMars Trace Gas Orbiter.
On Earth 95% of atmospheric methane is produced by living things, so the presence of methane in the Martian atmosphere has teased the possibility of life there.
Previously: ExoMars Trace Gas Orbiter Begins Mapping the Atmosphere of Mars Remember the Discovery of Methane in the Martian Atmosphere? Now Scientists Can't Find Any Evidence
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ExoMars returns first images from new orbit
The ExoMars Trace Gas Orbiter has returned the first images of the Red Planet from its new orbit.
The spacecraft arrived in a near-circular 400 km altitude orbit a few weeks ago ahead of its primary goal to seek out gases that may be linked to active geological or biological activity on Mars.
[...] The image captures a 40 km-long segment of Korolev Crater located high in the northern hemisphere. The bright material on the rim of the crater is ice.
[...] A long period of data collection will be needed to bring out the details, especially for particularly rare – or not even yet discovered – ingredients in the atmosphere. Trace gases, as hinted at from their name, are only present in very small amounts: that is, less than one percent of the volume of the planet's atmosphere. In particular, the orbiter will seek evidence of methane and other gases that could be signatures of active biological or geological activity. The camera will eventually help characterise features on the surface that may be related to trace gas sources.
Also at Space.com.
In 2003, scientists from NASA's Goddard Space Center made the first-ever detection of trace amounts of methane in Mars' atmosphere, a find which was confirmed a year later by the ESA's Mars Express orbiter. In December of 2014, the Curiosity rover detected a tenfold spike of methane at the base of the Gale Crater, and uncovered evidence that indicated that Mars has a seasonal methane cycle, where levels peak in the late northern summer.
The existence of methane gas on Mars has been long been held to be potential evidence for the existence of past or present life. So it was quite the downer last week (on Dec. 12th) when the science team behind one of the ESA's ExoMars Trace Gas Orbiter (TGO) spectrometers announced that they had found no traces of methane in Mars' atmosphere.
Maybe the Martians are hiding.
(Score: 2) by Azuma Hazuki on Friday April 12 2019, @06:59AM (3 children)
Perhaps there is a very, very thin distributed community of something akin to archaeobacteria several miles below the Martian crust, living a chemotrophic lifestyle that has methane as an end product?
I am "that girl" your mother warned you about...
(Score: 0) by Anonymous Coward on Friday April 12 2019, @08:28AM
Do they have a deep state too?
(Score: 2) by Immerman on Friday April 12 2019, @02:24PM
Indeed - I wouldn't even bet on the very, very thin part. If Mars ever had life, then all the underground chemovores and their predators are almost certainly still thriving, slowly moving deeper as the core cools. What do they care how (in)hospitable the surface of the planet is? Most of the gasses they produce would remain trapped underground, but some would trickle to the surface as conditions permitted. Seasonal underground ice deposits would likely trap such gasses beneath them, releasing a relatively short, high-concentration burst of gases as they thawed.
(Score: 3, Informative) by DeathMonkey on Friday April 12 2019, @05:44PM
One of the other articles I saw on this topic mentioned that methane can be created by purely geological processes so it's not a slam dunk indicator of life.
Not sure where I read that, though....
(Score: 2) by The Shire on Saturday April 13 2019, @01:20PM
It's not life folks. This is a product of serpentization which is a purely inorganic reaction also found on Earth (and even Saturn).
On the plus side, this is another indication that there was considerable amounts of water / brine on Mars at one point in it's history.