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Mars Express artist concept in orbit around Mars. A new analysis of the spacecraft data independently confirmed the first detection of methane by NASA's Curiosity mobile in 2013. Image via the DLR Institute of Planetary Research.
Where does the methane from Mars come from? This is one of the most intriguing mysteries for Mars scientists in recent years. Could the methane of Mars be the proof of … life?
At present, there is a correlated confirmation of significant detection of methane. This is the first time that an in situ measurement has been independently confirmed since orbit. Since landing in 2012, NASA's Curiosity rover has sometimes detected methane in the Mars atmosphere. The new study – led by Marco Giuranna of the National Institute of Astrophysics and the Institute of Astrophysics and Space Planetology in Rome, Italy – confirms that ESA's Mars Express orbiter has detected a spike in methane in June 2013 after Curiosity. The peer-reviewed finding was reported in Nature Geoscience April 2019. According to Dmitri Titov, scientist of ESA's Mars Express project:
Mars Express was the first to report a significant detection of methane in orbit around Mars and, 15 years later, we can announce the first detection of simultaneous methane and co-located with a mobile on the surface.
Why is methane on Mars so interesting for scientists? Write in Science Last year, Eric Hand called this gas the scent of life, mainly because some 16% of the Earth's annual methane emissions into the atmosphere come from the burps of cows. ESA explained:
The molecule attracts such attention because on Earth, methane is generated by living organisms, as well as by geological processes. Because it can be destroyed rapidly by atmospheric processes, any detection of the molecule in the Martian atmosphere means that it must have been released relatively recently, even if the methane itself was produced there. There are millions or billions of years and was trapped in underground tanks.
While spacecraft and telescopic observations from Earth have generally reported no or very few methane detections, or measurements made at the limit of the instrument's capabilities, a handful of parasitic peaks, as well as the seasonal variation related to its location in the crater Gale, ask the exciting question of how it is generated and destroyed at present.
The peak observed in June 2013 by Curiosity was about 6 ppb (parts per billion), while the day of detection of Mars Express was about 15 ppb. This is very little compared to methane levels in the Earth's atmosphere, but it remains important. In comparison, background levels of methane in the crater Gale [where Curiosity is exploring on Mars] tend to go from 0.24 ppb to 0.65 ppb. Paper:
Reports of methane detection in the Martian atmosphere have been intensely debated. The presence of methane could improve habitability and could even be a signature of life. However, no detection has been confirmed by independent measurements. We report here a firm detection of 15.5 ± 2.5 ppb by volume of methane in the Martian atmosphere over the Gale crater on June 16, 2013, by the Fourier planetary spectrometer aboard Mars Express, a day after the in situ observation of a peak of methane by the Curiosity rover. Methane has not been detected in other orbital passages. The detection uses improved observation geometry, as well as more sophisticated data processing and analysis, and is a simultaneous and independent detection of methane. We perform overall simulations of the Martian atmosphere … in order to identify a potential source region east of Gale Crater. Our independent geological analysis also indicates a source in this area, where Aeolis Mensae faults could extend over the proposed shallow ice of the Medusae Fossae Formation and occasionally release trapped gas under or in the ice. Our identification of a likely rejection site will guide future research on the origin of methane on Mars.
Grid of the area around the crater Gale where methane is most likely to come from, according to the new study. Image via ESA / Giuranna et al. (2019).
Although Curiosity's results are independent, the additional confirmation from Mars Express reinforces the findings and helps pinpoint the origin of the methane spike, as Giuranna explains:
In general, we did not detect any methane, apart from a definitive detection of approximately 15 parts per billion of methane volume in the atmosphere, a day after Curiosity reported an increase in methane. About six parts per billion.
Although parts per billion usually represent a relatively small amount, it is quite remarkable for Mars – our measure is an average of about 46 tons of methane. [51 U.S. tons] which was present in the 49,000 square kilometer area [19,000 sq miles] observed from our orbit.
So, a rover and an orbiter have both confirmed the peak of methane, but where does it come from? The Curiosity team assumed at the time that it was coming from somewhere north of the rover, but still inside the Gale crater, where the rover has been installed since 2012. But the new analysis indicates that it came more probably from outside the crater, about 310 miles (500 km) to the east. According to Giuranna:
Our new Mars Express data, taken one day after the Curiosity registration, modifies the interpretation of methane provenance, particularly when looking at global atmospheric circulation patterns as well as local geology. Based on geological evidence and the amount of methane we measured, we believe that it is unlikely that the source is located in the crater.
Illustration illustrating which processes could create and destroy methane on Mars. The methane probably comes from the surface and is released into the atmosphere by cracks below the surface. Image via ESA.
Two independent analyzes came to the same conclusion. The area around Gale Crater was divided into grids of 250 square kilometers [96 sq miles] to limit the location of the tip.
Researchers from the Belgian Royal Belgian Aerospace Institute (BIRA-IASB) in Brussels, Belgium, performed the first analysis, using computer simulations to create a million possible emission scenarios for each square, to predict the probability of methane emission for each of these squares. these places. The simulations were complete and took into account the measured data, the expected atmospheric circulation patterns as well as the intensity and duration of the methane releases, based on the geological phenomenon of "gas seepage".
Geologists from the National Institute of Geophysics and Volcanology of Rome (Italy) and the Planetary Science Institute of Tucson (Arizona) conducted the second analysis. This one focused on the identification of the physical characteristics of the ground that could be associated with infiltration of methane coming from the surface. These features are common on Earth, including tectonic faults, mud volcanoes, and natural gas fields. According to co-author Giuseppe Etiope:
We have identified tectonic faults that could extend below a proposed region to contain shallow ice. Since permafrost is an excellent anti-methane seal, it is possible that ice traps methane below the surface and frees it episodically along the faults traversing the ice.
Remarkably, we have seen that atmospheric simulation and geological evaluation, carried out independently of one another, suggested the same source region of methane. It's very exciting and largely unexpected.
Diagram illustrating the seasonal variation in the amount of methane detected by the Curiosity mobile, culminating in the hottest months. Image via NASA / JPL-Caltech.
Periodic or intermittent releases of methane from sources such as these would fit with the observations of various telescopes and spacecraft over the years. Co-author Frank Daerden added:
Our results support the idea that methane releases on Mars could be characterized by small transient geological events rather than a constantly replenishing global presence, but we also need to better understand how methane is eliminated from the atmosphere. atmosphere and how to reconcile Mars Express data. with the results of other missions.
The scientists hypothesized that the most likely source of methane would come from the subsoil, and these results seem to confirm this. Pockets of methane could be released periodically as a result of such minor geological events. Curiosity had also determined that methane releases near its location were seasonal, apparently associated with warming periods in the summer, which small quantities of trapped methane released from warming ice deposits could explain.
NASA's mobile device, Curiosity, detected methane concentration peaks in the atmosphere in 2013 and 2014. The Mars Express orbiter from ESA also confirmed the first of these results. Image via NAS / JPL-Caltech.
Finding the location of at least one point of methane is important, but it does not tell us How methane was created first. On Earth, living organisms produce the vast majority of methane, including underground. It can also come from a geological activity. Does life also produce Mars methane – the most likely microbes – or geology? We do not know yet and only other observations will help answer this question. There is also the question of what causes the rapid disappearance of methane. Meanwhile, the analysis of methane sources will continue, as Giuranna noted:
We will re-analyze more data collected by our instrument in the past, while continuing our ongoing monitoring efforts, including coordinating certain observations with the ExoMars Trace Gas Orbiter.
Trace Gas Orbiter (TGO) – part of the ESA ExoMars mission – unexpected discovery no methane during his first studies of the Martian atmosphere, but it is possible that he did not look at the right moment, because the methane bursts seem to be of a seasonal nature. Hopefully future observations will be more successful – the probe ships some of the most advanced instruments designed to analyze methane and other trace gases.
Conclusion: The origin of Mars methane is one of the most intriguing mysteries of the red planet. We still do not know if the methane is geological or biological – or maybe both – but with the new data from Mars Express and Curiosity, we are now starting to get closer to or methane comes from – an important step towards just determination what is creating it.
Source: Independent confirmation of a methane spike on Mars and a source region east of Gale Crater
Via ESA
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