Curiosity sheds new light on the mystery of methane on Mars

Curiosity sheds new light on the mystery of methane on Mars. The Tunable Laser Spectrometer (TLS) in Sample Analysis at the Mars Chemistry Laboratory (SAM) on NASA’s Curiosity rover detected atmospheric methane during four nighttime measurements at Gale crater on Mars, but not during the two-day measurements . Methane is not.

This day-night difference suggests that methane accumulates at night when it is contained near the surface of Gale Crater, but falls below the instrument’s detection limit during the day, which is carried out in the Trace Gas Orbiter ( TGO) of ESA. time of day by devices. Their results appear in the journal Astronomy & Astrophysics (Curiosity sheds new light).

Curiosity sheds new light

Mosaic of the Valles Marineris hemisphere of Mars projected in point perspective, a view that would be seen from a spacecraft. The distance is 1,550 miles (2,500 km) from the planet’s surface. The mosaic is made up of 102 Viking Orbiter images of Mars. Center-scene shows the entire Valles Marineris canyon system, more than 1,240 miles (2,000 km) long and 5 miles (8 km) deep, from Noctis labyrinthus, the west arch system to the west, extending to chaotic terrain. in the past.

Several great ancient river channels begin in the chaotic terrain in the north central valleys and run north. Three Tharsis volcanoes (dark red spots), each approximately 15.5 miles (25 km) high, are visible to the west. South of Valles Marineris there is a very old area covered with many impact craters. Image credit: NASA / JPL-Caltech.

methane on Mars

Mosaic of the Valles Marineris hemisphere of Mars projected in point perspective, a view that would be seen from a spacecraft. The distance is 1,550 miles (2,500 km) from the planet’s surface. The mosaic is made up of 102 Viking Orbiter images of Mars. Center-scene shows the entire Valles Marineris canyon system, more than 1,240 miles (2,000 km) long and 5 miles (8 km) deep, from Noctis labyrinthus, the west arch system to the west, extending to chaotic terrain in the past (Curiosity sheds new light).

Several great ancient river channels begin in the chaotic terrain in the north central valleys and run north. Three Tharsis volcanoes (dark red spots), each approximately 15.5 miles (25 km) high, are visible to the west. South of Valles Marineris there is a very old area covered with many impact craters. The Martian atmosphere is composed mainly of carbon dioxide (95%), nitrogen (3%), argon (1.6%), as well as fractions of oxygen and water.

The presence of methane in the Martian atmosphere was first detected in 2003. On Earth, methane is produced by microbes that help most animals digest plants. While there are no cattle on Mars, discovering methane there is exciting because it could mean that microbes were or are living on the planet. However, geological processes that involve the interaction of rocks, water and heat can also produce it.

Mars Chemistry Laboratory

But before identifying its source, planetary scientists must address a question that is haunting them: why do some instruments detect the gas and others don’t! For example, Curiosity has repeatedly detected methane just above the surface of Gale Crater. But TGO has not detected higher levels of methane in the Martian atmosphereWhen TGO came on board in 2016, it expected the orbiting team to report that there is a small amount of methane everywhere on Mars, said Dr. Chris Webster, TLS instrument leader, a researcher at NASA’s Jet Propulsion Laboratory.

The TLS instrument has measured an average of less than half a trillion methane content in Gale Crater. These measurements are marked by staggering peaks of up to 20 parts per billion volume but when the TGO team announced that it contained no methane, I was certainly surprised, Dr. Webster said. The researchers were surprised by the TGO findings and immediately set out to investigate the TLS measurements on Mars. Some experts suggested that the Curiosity rover itself was releasing gas.

So we looked at the correlations with the orientation of the rover, the ground, the crushing of rocks, the wheel falling, his name, Dr. Webster said. I can’t overstate the effort put into by the team to make sure those measurements are accurate, and they are (Curiosity sheds new light). The scientists hypothesized that the discrepancy between the methane measurements is narrowed by the time of day. Because it requires a lot of power, TLS works mainly at night when no other Curiosity instruments are in operation.

Noctis labyrinthus

Mars’ atmosphere is cold at night, so methane seeping from the ground tends to accumulate near the surface, where Curiosity can detect it, said Dr. John Moores, a planetary scientist at the University of York. The TGO, on the other hand, requires sunlight to signal methane about 5 km (3 miles) above the surface. Dr. Moores said that any atmosphere near the surface of a planet goes through a cycle during the day.

As warm air rises and cold air sinks, heat from the sun churns the atmosphere. Thus, methane that is confined near the surface at night is released into the wider atmosphere during the day, diluting it to undesirable levels. The authors immediately decided to test this prediction by first collecting high-precision daytime measurements.

Martian atmosphere

TLS measured methane continuously over the course of a Martian day, bracketing a night measurement with two daytime measurements. We predicted that methane should effectively drop to zero during the day, and our two-day measurements confirmed that, said SAM principal investigator Dr. Paul Mahafi, a researcher at NASA’s Goddard Space Flight Center.

TLS nighttime measurement fits well with the averages we’ve already established. So this is one way to address this huge discrepancy. While this study shows that methane concentrations rise and fall throughout the day on the surface of Gale Crater, planetary scientists have yet to solve the global methane puzzle on Mars.

Scientists are closer to explaining the mystery of Mars’ methane. Reports of the discovery of methane on Mars have fascinated scientists and non-scientists alike. On Earth, the microbes that help most animals digest plants produce a significant amount of methane. This digestion process ends when cattle release it into the air or expel the gas.

Mystery of Mars’ methane

While there are no cattle, sheep or goats on Mars, finding methane there is exciting because it could mean that microbes were or are living on the Red Planet. However, methane may have nothing to do with microbes or any other biology; Geological processes that involve the interaction of rocks, water, and heat can also produce it.

Before identifying the sources of methane on Mars, scientists must address a question that has been plaguing them: why do some instruments detect the gas and others don’t? For example, NASA’s Curiosity rover has repeatedly detected methane just above the surface of Gale Crater. But ESA’s ExoMars trace gas orbiter has not detected any high levels of methane in the Martian atmosphere (Curiosity sheds new light).

“When the Trace Gas Orbiter was brought on board in 2016, I expected the orbiter team to report that there is a small amount of methane everywhere on Mars,” the Tunable Laser Spectrometer (TLS) instrument said in the sample. Chief Chris Webster said. Analysis at the Mars Chemistry Laboratory (SAM) on the Curiosity rover.

NASA’s Jet Propulsion Laboratory

TLS has measured an average of less than half per billion of the amount of methane in Gale Crater. This is roughly the equivalent of a pinch of salt in a lap pool. These measurements are marked by staggering peaks of up to 20 parts per billion volume. But I was certainly surprised when the European team announced that it did not contain methane, said Webster, who is based at NASA’s Jet Propulsion Laboratory in Southern California.

The European orbiter was designed as the gold standard for measuring methane and other gases around the planet. Additionally, Curiosity’s TLS is so accurate that it will be used to detect fires on the International Space Station and to track oxygen levels in astronaut suits. It is also licensed for use in power plants, pipelines, and fighter jets, where pilots can monitor oxygen and carbon dioxide levels in their face masks.

However, Webster and the SAM team were surprised by the European orbiter’s findings and immediately set out to investigate the TLS measurements on Mars. NASA’s Curiosity rover took this selfie on June 15, 2018, the 2082nd Martian day or sun of the rover’s mission. A dust storm had reduced sunlight and visibility at the rover’s location, which was at the “Duluth” drill site north of Vera Rubin Ridge. A small hole is visible in the large rock to the left of the rover. The self-portraits are created using images taken by Curiosity’s Mars Hands Lens Imager.

journal Astronomy & Astrophysics

Some experts suggested that the rover itself was releasing gas. So we looked at correlations with the orientation of the rover, the ground, the crushing of rocks, the wheel dropping, whatever, Webster said. I can’t overstate the effort put into by the team to make sure those measurements are accurate, and they are. Webster and his team reported their results today in the journal Astronomy & Astrophysics.

As the SAM team was working to confirm their methane detection, another member of the Curiosity science team, planetary scientist John E. Moores posted an interesting prediction in 2019. “I took what some of my colleagues are saying very Canadian. Given this, in the sense that I asked the question: ‘What if both Curiosity and the Trace Gas Orbiter are correct?’ “Moores said (Curiosity sheds new light).

Moores, as well as other members of the Curiosity team studying wind patterns at Gale Crater, hypothesized that the discrepancy between methane measurements decreases with the time of day. Because it requires a lot of power, TLS works mainly at night when no other Curiosity instruments are in operation. Moores noted that Mars’ atmosphere is cold at night, so methane seeping out of the ground accumulates near the surface where Curiosity can detect it.

NASA’s Curiosity rover captured these drifting clouds on May 7, 2019, the 2400th Martian day of the mission, or sun. Curiosity used its black and white navigation cameras to take the photos. Clouds of water ice are shown here about 19 miles (31 kilometers) above the surface. On the other hand, the Trace Gas Orbiter needs sunlight to locate methane about 3 miles or 5 kilometers above the surface.

Any environment near the surface of a planet goes through a cycle during the day,” Moores said. As warm air rises and cold air sinks, heat from the sun churns the atmosphereThus, methane that is confined near the surface at night is released into the wider atmosphere during the day, diluting it to undesirable levels. “Then I realized that no instrument, especially an orbiter, would see anything,” Moores said.

daytime measurements

Immediately, the Curiosity team decided to test Moors’s prediction by first collecting high-precision daytime measurements. TLS measured methane continuously over the course of a Martian day, bracketing a night measurement with two daytime measurementsWith each experiment, SAM sucked in Martian air for two hours, continuously removing carbon dioxide, which makes up 95% of the planet’s atmosphere.

This left a focused sample of methane that TLS can easily measure by passing an infrared laser beam multiple times, which is tuned to use the exact wavelength of light absorbed by methane. Paul Mahaffey, SAM Principal Investigator based at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said: John predicted that methane should indeed drop to zero during the day, and our two-day measurements were confirmed.

The nighttime TLS measurement fits well with the average the team had already established. “So this is one way to address this huge discrepancy,” Mahfey said. Although this study shows that methane concentrations rise and fall throughout the day on the surface of Gale Crater, scientists have yet to solve the global methane puzzle on Mars. Methane is a stable molecule that is expected to remain on Mars for about 300 years before dissociating from solar radiation.

atmosphere

If methane continually seeps out of the same craters, which scientists suspect, the possibility that Gale does not seem geologically unique must have accumulated in the atmosphere in sufficient quantities for the Trace Gas Orbiter to detect it. Scientists suspect that something is destroying the methane in less than 300 years.

Experiments are underway to test whether dust-induced very low-level electrical discharges in the Martian atmosphere can destroy methane, or whether abundant oxygen on the Martian surface can destroy methane before reaching the upper atmosphere. We need to determine if a faster-than-usual destruction mechanism exists to fully collect the rover and orbiter data sets, Webster said.

Header Image: This photo was taken by the Mars Hand Lens Imager camera mounted on the arm of NASA’s Curiosity rover on March 19, 2017. The image helped mission team members observe the six o’clock position. Curiosity wheels during the 1641st Martian day, or sun, of the rover’s mission to Mars. credit: NASA / JPL-Caltech / MSSS. More information here.

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