"Curious" found Mars mysterious methane emissions

Is there life on Mars? The red planet may have an answer in the wind.

In the thin, icy atmosphere of Mars, the US "Curious" rover detected fluctuating traces of methane, which is often considered a sign of life. On December 17, Beijing time, the research team announced the discovery at the American Geophysical Union.

Curiously climbed over the surface of Mars into the Gaelic crater and slowly climbed to the top of a sedimentary rock called Sharp Mountain. There, methane is present at a background concentration of slightly less than one part per billion (1 ppb) atmospheric capacity. According to the latest news released by the National Aeronautics and Space Administration (NASA), the "Curious" sample analyzer measured the Martian atmosphere for 12 times in 20 months. However, for unknown reasons, the average of several peak methane emissions concentrations, It is about 10 times the background concentration.

Researchers say that further research on methane emissions in situ will help us determine whether methane gas is present or not, but it is unclear when and when these studies will go smoothly. The results of this discovery are published in the latest issue of Science.

The background value of methane concentration is different from that of a year ago.

“Many of the methane gases on Earth are produced from living things, and we have always hoped that 'methane on Mars' can be reduced to 'life on Mars.'” Chris Webster, senior researcher at NASA Jet Propulsion Laboratory and author of the paper Says, "But we haven't identified whether this high-concentration methane is an emission of geochemical components or is produced by Mars." Webster and his team pointed out that this unexpected methane eruption was on a rover. Produced in a very close to the north.

This finding is an exciting reversal of the results of the "Curious" release a year ago. The results of a year ago were based on data collected over 1/3 of Mars years, but ruled out the possibility of a large amount of methane gas in the Martian atmosphere. The "no value" result is now clarified because the actual background concentration of Mars methane is lower than the minimum operational testing capability of the detection equipment carried by Curiosity.

"Scientific American" magazine reported that in order to "sniff" the presence of methane, the "Curious" team insisted on finding it for a long time - they collected a whole year of Mars data, not only collecting "rich" Mars air. The sample also removes carbon dioxide and "magnifies" tiny traces of methane. In the end, they found a methane background concentration of one-billionth of the atmospheric concentration, that is, about 200 tons of methane gas flowing in the Martian atmosphere each year. Relatively speaking, there are billions of tons of methane per year in the Earth's atmosphere. flow.

Confirm that the source of methane emissions comes from living things

Although hot water produces methane when it flows through mineral-rich rocks, most of the earth's methane is produced from anaerobic bacteria that live in low-oxygen environments such as non-flowing water and animal gut. The extremely weak methane background on Mars is largely produced by ultraviolet radiation on carbon-rich meteorites and comet fragments and between planets.

However, this mechanism does not easily explain the methane flow found by Curious because it requires a recent meteorite impact or an air explosion near the Gaelic crater, and if such a thing happens, hover over Mars orbit. The detection spacecraft above the sky will certainly find such signs.

Another possibility is that the methane gas flow is not a small probability accident near the “Curious”, but it may also be the result of a large amount of methane emissions that occur away from the rover.

For more than a decade, many research teams have used the observations of noise generated by deep space telescopes or interstellar detectors on Earth, and have also reported signs of releasing large amounts of methane gas in the Martian atmosphere, ranging from 10 ppb to 60 ppb. In 2009, a team led by NASA's senior scientist at the Goddard Space Flight Center in Green Barth, M. Mumma, declared that huge methane plumes were regularly ejected from specific areas of the Martian surface.

Kevin Zanol, another team at the NASA Ames Research Center, questioned the authenticity of this methane jet. Zanol said that the effects of the Earth's atmospheric environment may contaminate the data obtained by the Mma team using astronomical telescopes, and that intermittent methane jets require a large chemical catalysis within the full Mars range that is almost impossible to exist.

The cyan-free atmosphere of the early detection of Curious is widely regarded as evidence to support this view, because even if a large amount of catalytic material that promotes methane causes methane eruption, it will be easily detected in the environment. The clues.

Although Mma’s statement in 2009 that a large amount of methane injection was found to have been over-exerted in the past few years, Mma still felt that there was something in Mars that was far from the detector releasing a large amount of methane. But he admits that the weakness of this view is that based on the current assumptions about the wind direction pattern in and around the Gaelic crater, there is no strong support for all the data. "We haven't figured out the release and persistence of methane on Mars," Mma said. "But on its hard shell, the results of this 'Curious' test are still exciting, after all, it's clear There is a source of methane emissions on Mars."

However, this source of emissions may also be the Rover itself, with a small amount of methane emitted from its components. "There is a lot of methane in the Mars, which is not controversial." Zanol wrote in the "Science" this article that will bring controversy in the future, the title is "The real problem is - methane Does the sample come from a rover or a Mars? 》

In response to this question, Webster said that the "Curious" team repeatedly checked all the Rover component indicators that may contaminate methane. In order to prevent the heavy wheels of the Rover from happening to destroy the gas-rich sediments, the team also carefully analyzed The "Curious" number passes through the rock samples of the area.

After repeated verification, they concluded that the methane flow detected by Curious was indeed a sign of a mysterious process that occurred somewhere near the current location of the rover.

Finding real life is not the focus of "Curious" to detect Mars

If the process is biological, then Mars microbes may be “snoring” in the shelter. Webster believes that it can find evidence and grasp the situation. “On Earth, bacteria are lazy and inefficient, they will be lighter. 15% of the carbon isotope C-12 is converted to the heavier carbon isotope C-13". If the “Curious” is lucky enough to observe another methane flow, it will be able to fine-tune the collected rich air samples and measure the ratio of C-12 and C-13 to distinguish whether the source is biological or abiotic. . Of course, this requires a lot of measurements and a longer abundance of air samples.

However, such a measurement will face enormous challenges for a Mars rover that is trying to climb the steep slopes of Sharp Mountain. The last "Curious" "sniff" to methane gas was 5 months ago. The researchers said: "We will continue to monitor methane, but unfortunately these experiments are very energy-intensive, knowing that there are many geological missions for the 'Curious' mission."

The mission of "Curious" was originally intended to study the signs of ancient life in Mars, not the signs of life today. Intensifying efforts to find more Martian methane gas will directly hinder the "Curious" to achieve its stated goals. Although Webster said that there are already thousands of times more sensitive than the methane detectors carried by Curious, it can easily detect potential life sources in gas, but such devices have until now Not included in the recent space exploration program of NASA and other space exploration agencies.

Future missions, such as the "outer Mars" orbiter and rover in Europe, and the cloned version of the "Curious" Rover, which NASA will launch in 2020, will carry out the necessary exploration and try Uncover the mystery of Mars methane emissions.

At the same meeting that posted the news, the Curious team also showed more evidence of early life – a variety of organic compounds found in a sample of Martian rock drills called “Cumberland” It is mainly composed of carbon, hydrogen and oxygen, but the specific "identity" is unknown. This is the first time that organic matter is found in the surface material of Mars. It proves that Mars in ancient times is warm and humid, more like the earth, and more suitable for life. Subsisting.

But is there still life on this red planet? Even if it is tilted in the speed and focus of future exploration, it will take another few years to get a clear answer.