The Curiosity Rover Discovered Organic Molecules on Mars. Does This Mean There Is Life?

(Non-text, this chapter is free, for everyone to read.)

According to foreign media reports, NASA held a press conference at 2 pm Eastern Time on June 7 (2 am BJ Time on June 8), announcing two important discoveries about Mars: 1. The Curiosity Mars rover found organic molecules in a 3 billion-year-old sedimentary rock close to the surface of Mars, indicating that ancient life may have existed on Mars;

2. It was found that the methane content in the Martian atmosphere has seasonal fluctuations, which may be related to modern Martian life. Although it is not enough to prove that there must be life on Mars, these discoveries are undoubtedly a good sign for future Martian surface and underground exploration missions.

Both new discoveries were published in the journal Science on June 8.

Organic molecules are composed of carbon and hydrogen, and may also include oxygen, nitrogen and other elements. Although usually associated with life, organic molecules can also be produced by non-biological processes and are not necessarily evidence of the existence of life.

"Mars is telling us with these new discoveries: Stay on track and keep looking for evidence of life," said Thomas Zurbuchen, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. "I'm confident that current and future missions will yield more surprising discoveries on Mars."

"Curiosity has yet to determine the source of these organic molecules," said Jennifer Eigenbrode of NASA's Goddard Space Flight Center, lead author of one of the two papers. "Whether the organic matter in the Martian soil is a record of ancient life, food for organisms, or unrelated to life, it provides chemical clues about the Martian environment and evolution."

Although the surface of Mars is not hospitable to life today, there is clear evidence that the ancient Martian climate once allowed liquid water to gather on the surface and form lakes. And as far as we know, liquid water is a prerequisite for life. Data collected by Curiosity show that billions of years ago, a lake in Gale Crater had all the materials necessary for life, including chemical building blocks and energy sources.

"The surface of Mars is exposed to cosmic radiation. Radiation and harsh chemicals can decompose organic matter," said Eigenbrod. "The discovery of ancient organic molecules in the top 5 centimeters of sedimentary rocks formed during the habitable period of Mars is a good sign for us. In future missions, we will continue to dig down to further understand the sources of organic molecules on Mars."

"ESA's ExoMars rover will dig deeper, up to two meters underground," Eigenbrod explained, "so it is possible to dig rocks that have not been subjected to severe space radiation."

"The ExoMars rover may also find existing life. But even if it doesn't find it, just analyzing the changes in organic matter from the surface to deep underground is enough to produce amazing discoveries."

Methane on Earth can exist in the form of "combustible ice." What about Mars?

In the second paper, scientists describe seasonal fluctuations in methane levels observed in the Martian atmosphere over the past three Martian years (about six Earth years). This fluctuation was detected by Curiosity's Sample Analysis at Mars.

The methane may come from chemical reactions between water and rocks, but scientists have not ruled out the possibility of biological involvement. Previously, scientists have only found methane in the Martian atmosphere in the form of large, irregular plumes. The new findings show that the small amount of methane contained in Gale Crater increases, peaks in warm summers, and then decreases again in winter, year after year.

This discovery is important because it will help narrow down the possible sources of methane. Methane on Earth is mainly related to biological activity, from wetlands, farmland, livestock, etc. It is not yet possible to confirm whether methane on Mars is related to biology. But the seasonal fluctuations in methane found this time may rule out some geological explanations.

"This is the first time we have found something repetitive in our observations of methane, so it helps us understand it," said Chris Webster of NASA's Jet Propulsion Laboratory, the lead author of the second paper. "This is all thanks to Curiosity's 'longevity'. Without its long service, we would not have discovered this seasonal variation."

Methane in the Martian atmosphere has always been a hot topic in scientific research. Methane cannot remain in the atmosphere for a long time. Since methane is always present in the Martian atmosphere, there must be a continuous source of methane. Given the connection between methane and life on Earth, scientists must solve this Martian mystery.

Since Curiosity landed in Gale Crater at the Martian equator in 2012, it has been looking for traces of methane in the Martian atmosphere. It was found that the methane content in the northern hemisphere winter is only slightly higher than 0.2 parts per billion, but it rises to 0.6 parts per billion in the summer. The research team believes that this methane may be stored in the form of ice

The team has not been able to confirm the source of the methane, but believes that one explanation can be ruled out - that sunlight can break down carbon-containing molecules (organic molecules) in meteorites on the Martian surface, thereby producing methane. Dr. Webster pointed out that the seasonal variation in ultraviolet light is not large enough to cause such a change in methane concentration.

This low-angle selfie of Curiosity records the scene of drilling a target rock sample in Mount Sharp in Gale Crater.

In order to search for organic matter in the Martian soil, Curiosity drilled samples of sedimentary rocks (also known as mudstones) in four areas of Gale Crater. These mudstones were formed by sediments that accumulated at the bottom of ancient lakes over billions of years. The drilled rock samples were analyzed by the Sample Analyzer for Mars instrument. The instrument heats the samples in an oven at more than 500 degrees Celsius, which releases organic matter from the powdered rock.

In the material released from the mudstone samples, Sample Analyzer for Mars detected small organic molecules, fragments of large organic molecules that do not easily evaporate. Some of the fragments contain sulfur. Eigenbrod said that the fragments are more stable and durable because of the presence of sulfur, just as sulfur is added to tires to increase durability.

The results also showed that the content of organic carbon was on the order of 10 parts per million, or even more. This is close to the carbon content detected in Martian meteorites and about 100 times the organic carbon content previously detected on the surface of Mars. The molecules identified this time include thiophene, benzene, toluene, etc., as well as short carbon chains such as propane and butene.

In 2013, the Mars Sample Analyzer found some chlorine-containing organic molecules in the deepest rocks of Gale Crater. This new discovery further enriches the types of molecules found in ancient lake sediments on Mars and helps explain why these molecules have survived to this day.

After the discovery of methane in the Martian atmosphere and the discovery of organic molecules preserved in ancient times near the surface, scientists have greatly strengthened their confidence that NASA's 2020 Mars rover and ESA's "Mars Space Biology" (ExoMars) rover will also find more organic matter on the surface and shallow surface of Mars.

"Do these findings indicate that there is life on Mars?" Michael Meyer, chief scientist of NASA's Mars Exploration Project, asked. "We don't know yet. But these results show that we are on the right track."

The research was sponsored by the Mars Exploration Mission of the Science Mission Directorate at NASA Headquarters. The Goddard Space Flight Center provided the Mars Sample Analyzer. The Jet Propulsion Laboratory was responsible for the construction of the rover and managed the project for the Science Mission Directorate.

……

……

A few comments from the author:

The organic matter analysis instrument of "Curiosity" is actually a relatively simple instrument. It decomposes large molecular organic matter by heating, allowing them to release, and then analyze simple organic molecules.

For example, this time we got: thiophene, benzene, toluene, etc.

The organic matter that is really hidden in the soil is likely to be more complex than these because of heating.

It is not clear whether it is life.

Some people will definitely say: Why not launch a more powerful detection instrument? This organic matter analysis instrument is too simple, right?

Because Curiosity is already the limit of current technology, or close to the limit. It was launched in 2011, and now it is 2018. In just 7 years, there has not been a particularly big qualitative change in aerospace engineering. Our science is not as advanced as we think.

It may take decades to really confirm whether there is life.

I hope our country can also contribute to this project.

Also, if life is really discovered on Mars, or if life once existed, it may not be a good thing for us (human beings).

The more complex life is discovered, the worse it is...

Because that means there is life everywhere in the starry sky... This problem has been explained in the novel, so I won’t repeat it again.