Artist's impression of the ExoMars TGO orbiter which attempts to solve the Mars methane mystery unsuccessfully. Credit: ESA

Mars Methane Mystery Deepens

While the Mars orbiters fail to detect methane on Mars, the Curiosity rover continues to record emissions from the surface.

The Russian-European probe “ExoMars-TGO” did not detect even minimal traces of methane and two other hydrocarbons emitted by representatives of terrestrial life in the atmosphere of Mars, as well as molecules of phosphine, phosphorus and hydrogen compounds of potentially biogenic origin. 

Everything you need to know about the Mars Methane Mystery

1. The Russian-European mission “ExoMars-TGO” has been studying the atmosphere of Mars for three years, measuring the concentrations of various gases in the air of the Red Planet. One of its main tasks is to assess the concentration of methane in the Martian atmosphere and search for its possible sources, as well as many other gases.

2. The first results of long-term observations unexpectedly indicated that during the first full year of operation, the ExoMars-TGO instruments did not record any traces of methane in the atmosphere of Mars, even in the smallest quantities, despite the fact that at the same time, the Curiosity rover recorded methane emissions on several occasions in the Gale Crater.

Summary of the previous measurement attempts to solve the Mars methane mystery. Credit: ESA
Summary of the previous measurement attempts to solve the Mars methane mystery. Credit: ESA

3. Planetary scientist Franck Montmessin and his colleagues continued their observations with the Russian ACS instrument, as well as three other scientific instruments installed aboard the ExoMars-TGO.

4. As part of these measurements, scientists tracked not only the concentration of methane but also two other hydrocarbons, ethane and ethylene, which can be produced by terrestrial microbes or their Martian counterparts.

5. In addition, last year, scientists began measuring concentrations of phosphine, another potentially biogenic gas that was believed to have been found in the atmosphere of Venus. As the researchers note, both those and other searches ended unsuccessfully – the ultrasensitive sensors of the probe failed to record any significant amounts of all four gases.

Searching for other biomarkers on Mars. Credit: ESA
Searching for other biomarkers on Mars. Credit: ESA

6. In the case of methane, this means that its concentration in the atmosphere of Mars cannot exceed 0.02 parts per million, which is several orders of magnitude less than the values ​​obtained by the Curiosity rover during methane emissions in mid-summer 2019.

7. Nearly similarly low values ​​of about 0.1-0.7 ppb were recorded during the first observations of the concentrations of ethane and ethylene, as well as phosphine.

8. Such low concentrations of these gases in the air of Mars indicate that if they are emitted into its atmosphere, then this happens sporadic and in extremely small quantities.

9. In favor of this, in particular, is evidenced by the fact that the European device NoMAD, installed onboard the probe, did not find a single point source of methane emissions on the planet’s surface in two thousand attempts to detect them.

10. Such discoveries, Montmessin and colleagues note, deepen the mystery of the Curiosity rover’s detection of methane emissions. Scientists hope that sending the European rover Rosalind Franklin and the Russian landing platform Kazachok to Mars will help find the first explanations for the existence of this anomaly in the next one or two years.

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ESA. (n.d.). ExoMars orbiter continues hunt for key signs of life on Mars.
Knutsen, E. W. (2020, December 15). Comprehensive investigation of Mars methane and organics with ExoMars/NOMAD. Icarus.
Montmessin, F. (n.d.). A stringent upper limit of 20 pptv for methane on Mars and constraints on its dispersion outside Gale crater.
Olsen, K. S. (n.d.). Upper limits for phosphine (PH3) in the atmosphere of Mars.

Written by Vladislav Tchakarov

Hello, my name is Vladislav and I am glad to have you here on Curiosmos. As a history student, I have a strong passion for history and science, and the opportunity to research and write in this field on a daily basis is a dream come true.

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