Research

The Martian orbital probe ExoMars-TGO did not find methane in the atmosphere of the Red Planet

Spacecraft Trace Gas Orbiter (TGO)the European-Russian mission ExoMars has been working in the orbit of the Red Planet for a year now. During this time, he managed to do a lot of useful things: he made a more detailed map of the distribution of water under the surface of the planet, studied the effect of global dust storms on the atmosphere of Mars, and also ... did not find any traces of methane in its atmosphere, which deepened the mystery of its discovery with the tools of the rover “Curiosity” of the US Aerospace Agency NASA and sensors of the Mars Express probe of the European Space Agency (ESA), which were previously reported.

The discovery of methane on Mars has become a reala sensation. On Earth, almost all the reserves of this gas in the atmosphere are of biological origin (part, however, associated with geochemical processes), and it is rapidly destroyed as a result of the interaction of its molecules with the sun's rays and oxygen. For this reason, many scientists have suggested that Martian microbes can be the source of Martian methane.

Just last week, NASA and ESA announcedthat both the Curiosity rover and the Mars Express orbiter found large methane emissions one day apart in 2013 and were even able to triangulate the most likely source of emissions. However, the latest observations from the TGO spacecraft, published by Nature, show a completely different picture of the content of this gas in the atmosphere of the Red Planet.

The researchers analyzed the data of the deviceTrace Gas Orbiter (TGO), collected between April and August last year. To increase the accuracy of measuring trace gas concentrations, TGO uses the solar eclipse method - it measures the absorption spectrum of the atmosphere at sunset and sunrise. This makes it possible to reduce the noise level in the recorded spectrum and to increase the optical path of the rays by ten times (that is, the volume of the atmosphere in which the gas concentration is measured). These measurements are carried out by the orbital probe using ACS and NOMAD spectrometers.

Despite the relatively short durationobservations, the probe was able to measure the concentration of methane in almost a hundred points above the surface of the Red Planet. Most of these measurements relate to the circumpolar regions, but several points also capture equatorial latitudes, in particular, the area of ​​the Gale crater, where the Curiosity rover found a large emission of gas into the atmosphere. Analysis of the data obtained shows that at all these points TGO noted a concentration of no more than 0.15 billionths of a volume, taking into account the errors. This is a hundred times less than Mars Express data and ten times less than Curiosity data.

A map of the area that TGO was doing to calculate the concentration of methane in the atmosphere

“We have increased the accuracy of measurements by severalorders of magnitude compared to the SAM tool on board the rover Curiosity. We managed to find traces of water in the extremely dry atmosphere of Mars, but we never found even minimal amounts of methane, which would be above the background noise level, not to mention those quantities that were recorded by the NASA rover, ”comments one of the scientists. ExoMars-TGO Mission Leaders Oleg Korablev from the Space Research Institute of the Russian Academy of Sciences.

"We do not criticize the measurements that were takenother teams need to understand that we made observations last summer and autumn, and the rover and probe five years ago. On the other hand, now it is even more difficult for us to explain where this methane could have disappeared, given the mechanisms that can destroy it, ”the scientist adds.

In mid-2018, Mars went downglobal dust storm that cost “life” to one of the NASA aerospace agency mars rovers - Opportunity. Watching this event from above, the TGO orbiter had an excellent opportunity to figure out the impact of such giant storms on the planet’s atmosphere. Data analysis was conducted by another group of scientists led by Ann Vandale. The results of their research were also published in the journal Nature.

Volumetric concentrations of water and "light heavy" water and their ratio depending on the height. Lines of different colors describe different moments relative to the storm on May 30

Scientists have measured the vertical distributiondust, water and "light heavy" water (in its molecules contains one atom of hydrogen and deuterium) to a height of 90 kilometers above the surface. Analysis of the data showed that before the dust storm of May 30, 2018, the “light heavy” water practically disappeared from altitudes of more than 40 kilometers, which indicates the formation of water-ice clouds. However, during the storm this concentration increased again, which means that the newly formed clouds heated up, melted and collapsed. Scientists note that these processes can further accelerate the circulation of substances through the atmosphere.

Water is contained not only in the atmosphere of the Redthe planet, but also beneath its surface. Using the FREND tool, the TGO probe from May to September last year conducted several scans of the surface of Mars, thanks to which scientists were able to update the global map of water distribution in the soil to a depth of 1 meter. The instrument was used to observe how the cosmic rays interact with the surface. In particular, the device measured the speed of reflection (rebound) of neutrons from the surface - hydrogen contained in the form of ice, as well as hydrated minerals slow them down, allowing the device to determine the quantitative water content in a particular region.

Subsurface water distribution map on Mars created with the TGO

The results were similar to the conclusions.previous observations. The largest concentration of water is in the polar regions (in particular, near the North Pole of the planet), while the rest of the planet is covered with alternating "wet" and "dry" regions. The work of the FREND tool has not yet been completed, but scientists have already received the most detailed map of the distribution of water on the planet.

“In just 131 days of operation, we were able tomany times more detailed map, compared with the one that was created on the basis of 16-year observation data by the Mars Odyssey spacecraft, ”commented Igor Mitrofanov, lead author of a study on the detail of water distribution on Mars.

“The data is constantly updated. Over time, we will get a complete map of the distribution of subsurface Martian waters. This is important not only for determining the water-rich regions of the planet, but also for understanding the general evolution of Mars. In addition, the data will definitely be useful for future missions to explore the Red Planet, ”adds the scientist.

You can discuss the article in our Telegram-chat.