ESA’s ExoMars Trace Gas Orbiter has discovered new gas firms in Mars. These unlock new secrets about the Martian atmosphere and allow a more precise determination of whether there is methane, a gas associated with biological or geological activity, on the planet.
The Trace Gas Orbiter (TGO) has been studying the red planet from orbit for more than two years. The mission aims to understand the mixture of gases that make up the Martian atmosphere, with a special focus on the mystery surrounding the presence of methane there.
Meanwhile, the spacecraft has now seen never-before-seen ozone signatures (O3) and carbon dioxide (COtwo), based on a full Martian year of observations from his sensitive Atmospheric Chemistry Suite (ACS). The findings are reported in two new articles published in Astronomy and astrophysics, one directed by Kevin Olsen from the Oxford University, UK, and another led by Alexander Trokhimovskiy of the Space Research Institute of the Russian Academy of Sciences in Moscow, Russia.
“These characteristics are puzzling and surprising,” says Kevin.
“They are over the exact wavelength range where we expected to see the strongest signs of methane. Before this discovery, COtwo the feature was completely unknown, and this is the first time that ozone has been identified on Mars in this part of the infrared wavelength range. “
The Martian environment is dominated by COtwo, which scientists observe to measure temperatures, track seasons, explore air circulation, and more. Ozone, which forms a layer in the upper atmosphere on both Mars and Earth, helps keep atmospheric chemistry stable. Both COtwo And ozone has been seen on Mars by spacecraft like ESA’s Mars Express, but the exquisite sensitivity of the ACS instrument at TGO was able to reveal new details about how these gases interact with light.
This graph shows an example of measurements made by the MIR Atmospheric Chemistry Suite (ACS) instrument on ESA’s ExoMars Trace Gas Orbiter (TGO), which presents the spectral signatures of carbon dioxide (CO2) and ozone (O3).
The bottom panel shows the data (blue) and the best-fit model (orange). The upper panel shows the modeled contributions of a variety of different gases for this spectral range. The deepest lines come from water vapor (light blue). The strongest O3 characteristic (green) is on the right, and different CO2 lines (gray) appear on the left. The locations of strong methane (orange) characteristics are also shown in the modeled contributions, although methane is not observed in the TGO data. Credit: K. Olsen et al. (2020)
Observing ozone in the range where TGO searches for methane is a totally unexpected result.
Scientists have mapped how Martian ozone varies with altitude before. So far, however, this has been done largely through methods that rely on gas signatures in the ultraviolet, a technique that only allows measurement at high altitudes (more than 20 km above the surface). ).
The new ACS results show that it is possible to map Martian ozone also in the infrared, so its behavior can be tested at lower altitudes to build a more detailed view of the role of ozone in the planet’s climate.
This graph summarizes important attempts to measure methane on Mars. Earth-based telescopes, ESA’s Mars Express from orbit around Mars, and NASA Curiosity located on the surface of Gale Crater have reported on methane; They also reported measurement attempts with very little methane detected. More recently, the ESA-Roscosmos ExoMars Trace Gas Orbiter reported an absence of methane and provided a very low upper limit. Credit: ESA
Unraveling the mystery of methane
One of TGO’s key goals is to explore methane. To date, signs of Martian methane, tentatively spied on by missions including ESA’s Mars Express from orbit and POTThe Curiosity rover on the surface is variable and somewhat enigmatic.
This graph shows some of the possible ways that methane could be added to or removed from the atmosphere. How methane is created and destroyed on Mars is an important question to understand the various detections and non-detections of methane on Mars, with differences in both time and location. Although it constitutes a very small amount of the general atmospheric inventory, methane in particular contains key clues to the planet’s current state of activity. Credit: ESA
Although it is also generated by geological processes, most of the methane on Earth is produced by life, from bacteria to livestock and human activity. Therefore, detecting methane on other planets is very exciting. This is especially true given that gas is known to decompose in around 400 years, meaning that any methane present must have been produced or released in the relatively recent past.
“Discovering an unforeseen COtwo the signature where we look for methane is significant, ”says Alexander Trokhimovskiy. “This signature could not be taken into account before, and therefore may have played a role in detecting small amounts of methane on Mars.”
The observations analyzed by Alexander, Kevin, and their colleagues were made primarily at different times than those supported by Martian methane detections. Also, the TGO data cannot represent large columns of methane, only smaller amounts, so there is currently no direct disagreement between missions.
This graph shows a new CO2 spectral characteristic, never before observed in the laboratory, discovered in the Martian atmosphere by the MIR Atmospheric Chemistry Suite (ACS) instrument at ESA’s ExoMars Trace Gas Orbiter (TGO).
The graph shows the full extent of the magnetic dipole absorption band of the sixteenOR12CsixteenMolecule O (one of the various CO ‘isotopologists’two)
The upper panel shows the ACS MIR spectra (shown in black) along with the modeled contribution of COtwo and HtwoO (shown in blue); The model is based on the HITRAN 2016 database.
The bottom panel shows the difference between data and model, or residuals, revealing the structure of the absorption band in detail. The calculated positions of the spectral lines are marked with arrows, in different colors that correspond to different ‘branches’ of the absorption band (red represents the P branch, green for the Q branch and blue for the R branch).
Credit: A. Trokhimovskiy et al. (2020)
“In fact, we are actively working on coordinating measurements with other missions,” says Kevin. “Instead of contesting any previous claims, this finding is a motivation for all teams to take a closer look: the more we know, the deeper and more accurately we will be able to explore the atmosphere of Mars.”
Realizing the potential of ExoMars
Leaving methane aside, the findings highlight how much we will learn about Mars as a result of the ExoMars program.
“These findings allow us to build a more complete understanding of our planetary neighbor,” adds Alexander.
Mars is about half the size of Earth by diameter and has a much thinner atmosphere, with an atmospheric volume less than 1% that of Earth. The atmospheric composition is also significantly different: mainly based on carbon dioxide, while the Earth is rich in nitrogen and oxygen. The atmosphere has evolved: evidence on the surface suggests that Mars was once much warmer and wetter. Credit: ESA
“Ozone and COtwo they are important in the atmosphere of Mars. By not taking these gases into account properly, we run the risk of mischaracterizing the phenomena or properties we see. “
Furthermore, the surprising discovery of the new COtwo Band at Mars, never before seen in the lab, provides an exciting insight for those who study how molecules interact with each other and with light, and search for the unique chemical footprints of these interactions in space.
Together, these two studies take a significant step toward revealing the true characteristics of Mars: toward a new level of accuracy and understanding, “says Alexander.
Successful collaboration in the search for life
As its name suggests, the TGO aims to characterize any trace gas in the atmosphere of Mars that may arise from active geological or biological processes on the planet and to identify its origin.
Artist impression of the ExoMars 2020 rover (foreground), the surface science platform (background), and the Tracing Gas Orbiter (above). Not to scale. Credit: ESA / ATG medialab
The ExoMars program consists of two missions: TGO, which launched in 2016 and will unite with the Rosalind Franklin rover and the Kazachok landing pad, which will launch in 2022. These will bring complementary instruments to ACS to the Martian surface, examining the atmosphere of the planet from a different perspective, and shares the central objective of the ExoMars program: to look for signs of past or present life on the Red Planet.
“These findings are the direct result of a hugely successful and ongoing collaboration between European and Russian scientists as part of ExoMars,” says ESA TGO project scientist Håkan Svedhem.
“They set new standards for future spectral observations, and will help us paint a more complete picture of the atmospheric properties of Mars, including where and when methane can be found, which remains a key question in the exploration of Mars.”
“Furthermore, these findings will provoke a comprehensive analysis of all the relevant data we have collected to date, and the prospect of a new discovery in this way is, as always, very exciting. Every piece of information revealed by ExoMars Trace Gas Orbiter marks progress toward a more accurate understanding of Mars, and takes us one step closer to unraveling the planet’s lingering mysteries. “
More information
“First detection of mid-infrared ozone on Mars: implications for methane detection” by KS Olsen et al. (2020) (DOI: 10.1051 / 0004-6361 / 202038125) and “First observation of the CO magnetic dipoletwo absorption band at 3.3 μm in the atmosphere of Mars by the ExoMars Trace Gas Orbiter ACS instrument ”by A. Trokhimovskiy et al. (2020) (DOI: 10.1051 / 0004-6361 / 202038134) are published in Astronomy and astrophysics.
The studies used the Mid-InfraRed (MIR) channel of the Atmospheric Chemistry Suite (ACS) on the ExoMars Trace Gas Orbiter (TGO), reporting the first observation of 3000–3060 cm.-one ozone (O3) band and the discovery of 3300 cm-onesixteenOR12CsixteenOr magnetic dipole band (overlapping 2900–3300cm-one methane ν3 absorption band) on Mars.
ExoMars is a joint effort of the European Space Agency and Roscosmos.
The ACS instrument is led by the team of Principal Investigators from the Space Research Institute (IKI) of the Russian Academy of Sciences (RAN) in Moscow, Russia, assisted by the team of Co-Principal Investigators from CNRS / LATMOS, France, and co-researchers from other ESA Member States.
