NASA’s Curiosity Takes Step Toward Solving Mars Methane Mystery

The wheels of the Mars Curiosity Rover
The wheels of NASA’s Curiosity journey over the Martian panorama in Gale Crater. This picture was taken by a digicam on the rover’s arm.
NASA / JPL-Caltech / MSSS

Researchers already suspected it, however now they’ve proof. The focus of methane above Gale Crater, the touchdown web site of the Curiosity rover, adjustments from day to nighttime. It goes from low however measurable ranges through the night time to concentrations close to zero through the day. That day by day cycle might assist clarify why completely different devices had been seeing, and never seeing, methane.

Scientists have spent a long time chasing methane on Mars. On Earth, the gas is usually a signal of microbial exercise, however it will also be a product of chemical reactions between liquid water and sure minerals. Finding methane within the Martian ambiance might reveal that comparable processes are occurring underground on the Red Planet.

Curiosity first sniffed methane on Mars on June 15, 2013. Since then it has discovered that background ranges differ between 0.2 and 0.7 components per billion in quantity (ppbv). Subsequent measurements counsel that methane abundances may observe a seasonal sample, with extra of the gas current through the summer season and fewer within the winter (though a current statistical evaluation says that interpretation may not be statistically sound).

Curiosity additionally detected occasional peaks in methane focus, referred to as plumes, which reached a most of 20.5 ppbv on June 19, 2020. In 2013, one in every of these plumes was detected simultaneously by Curiosity and the European Space Agency (ESA) Mars Express orbiter.

Scientists speculate that methane might be leaking from the Martian underground, the place it’s both generated by ongoing processes or saved in reservoirs shaped within the distant previous. Alternatively, the gas may kind on the floor when solar ultraviolet radiation breaks up meteoritic mud that falls onto the planet from outer space.

methane creation possibilities on Mars
There are a number of methods so as to add methane to Mars’s ambiance (and take it away once more). Although microbes are probably the most thrilling risk, different seemingly sources embody reactions between water and the minerals olivine or pyroxene, or solar ultraviolet radiation breaking apart meteoritic mud on the planet’s floor.
NASA / JPL-Caltech / SAM-GSFC / Univ. of Michigan

But in April 2019, the ESA’s ExoMars Trace Gas Orbiter, a spacecraft particularly designed to measure vanishingly small concentrations of gases within the Martian ambiance, failed to find signs of methane after a number of months of operation. A collaborative mission between ESA and Roscosmos, TGO seems to be at daylight because it travels by means of the higher layers of the ambiance, 5 kilometers above the bottom, and will be capable to detect particle concentrations as little as 0.05 ppbv. That’s 10 instances lower than what was being routinely measured by Curiosity.

After months of heated debate, a gaggle of researchers led by John Moores (York University, Canada), realized that the discrepancy might boil right down to the time of day the measurements had been taken. “What if they’re both right, what does that tell us about Mars?” Moores questioned. “Then you’ve got to have methane changing over the course of the day.”

Curiosity’s chemistry lab is an influence hog. Every time it does a methane run, the Tunable Laser Spectrometer (TLS) contained in the Sample Analysis at Mars (SAM) pumps in Martian air for a number of hours. For that purpose, these runs have at all times been performed at night time, when no different devices are working. The Martian ambiance is cool and calm at night time, Moores famous, making it extra seemingly that it’s going to maintain onto any molecules slipping out from an underground supply. But whereas Curiosity was capable of detect the methane on the floor, the TGO was trying on the ambiance at sundown, after a whole day of Sun-driven atmospheric mixing, when the methane might already be too diluted to choose up.

Artist's depiction of Schiaparelli lander separating from the Trace Gas Orbiter
An artist’s impression of the ESA’s ExoMars Trace Gas Orbiter hovering over Mars after separating from its lander, Schiaparelli.
ESA/ATG medialab

To check the thought, the Curiosity workforce tried a few methane runs through the day. TLS bracketed one nighttime measurement with two daytime ones. The nighttime measurement yielded 0.52 ppbv, in step with earlier outcomes, whereas the 2 daytime measurements picked up no methane in any respect, confirming Moores’s prediction.

“We are sure that the ground in Gale crater is leaking methane, even at the low levels observed,” says Chris Webster (Jet Propulsion Laboratory), principal investigator of the TLS instrument. “Our new data take an important step toward reconciling the Curiosity and ExoMars data sets.” Webster and his workforce reported these results in the June Astronomy & Astrophysics.

Even if they’re proper, although, the speed of methane seeping from underground reservoirs into the ambiance should be very low. Moores and his colleagues estimated {that a} most of two.8 kilograms of methane escaping from Gale Crater day-after-day might clarify Curiosity’s measurements with out growing world ranges above TGO’s 0.05 ppbv detection restrict.

Then once more, it’s impossible that Gale Crater is the one place on Mars that leaks methane. If all the same craters on Mars spewed methane on the similar charge, the gas would over time construct as much as ranges TGO might detect. Methane molecules ought to survive for a mean of 300 years within the Martian ambiance earlier than solar radiation tears it aside, however TGO’s nondetection suggests one thing else is occurring. “Methane would have to be destroyed much more rapidly,” Moore says.

gale crater shown with Curiosity landing site.
A birds eye view of Gale Crater, the place methane detections (and non-detections) had been made by NASA’s Curiosity rover. This picture is a composite of knowledge from three Mars orbiters. The crater itself is sort of 154 km (96 mi) in diameter. Curiosity’s touchdown spot is denoted by the ellipse.
NASA / JPL-Caltech / ESA / DLR / FU Berlin / MSSS

Experiments are underway in a number of labs on Earth to find out what may very well be destroying methane. One risk is that small electrical discharges between suspended mud grains may very well be accountable. Another risk is that the gas is reacting with the oxygen-rich Martian floor in methods not predicted by present photochemical fashions. Maybe methane is simply getting caught to the mud floating within the ambiance.

Moores thinks we’d like extra measurements from the bottom. Curiosity has made about 16 measurements in a decade. “It’s a very coarse data set and you can imagine that it must be difficult to figure out what happens over the day if you only measure every six months.”

“Neither the Perseverance or Chinese rovers are able to measure Mars methane at any level,” Webster says. He suggests {that a} mini-TLS, both launched on an impartial mission or piggybacking on a deliberate future mission, might determine how a lot and the way typically methane is launched to assist settle its supply.


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