Life on Mars, from Viking to Curiosity

After midnight, in a stuffy room in Pasadena, in July 1976, members of the Viking program team, hunched over, sat around a massive monochrome monitor, and eagerly awaited the arrival of the first data from the world's first successful Martian probe, the only probe specifically designed to search for life. Over the next few weeks, each of the Viking life search experiments produced amazing results. The data was slowly transferred to the Control Center, and gradually it became clear that carbon dioxide was released as a result of the addition of organic components to the Martian soil, although this did not happen when the mixture was very hot. This was a sign of life - the same thing happened when this experiment was performed on Earth. When water was added to the soil, oxygen was released, just like on Earth. Remote probe in search of life found its signs in the first two experiments.

However, controversy intensified after the fourth experiment received ambiguous data. A statement about having life on Mars would be unprecedented. If scientists were wrong, they would never be able to justify themselves. But the results of three of the four experiments of the primitive descent vehicle "Viking" could be interpreted as a positive test for the presence of microbes, because they produced the same result as thousands of times repeated experiments on Earth. Researcher Patricia Strath said to another member of the team, Gil Levin: “This is life!”



However, the fourth experiment, using a gas chromatograph of the same type that James Lovelock used, and a mass spectrometer, a delicate instrument for measuring the size of molecules, showed no existence of life — and in general any organic matter — on Mars. This result was overwhelming: organic exists everywhere in space, on asteroids, comets and meteors, and interstellar dust. Moreover, the experiment showed that the surface of Mars was poisonous or self-sterilizing. Scientists had a heated argument, and NASA eventually chose a cautious approach to the problem. The agency decided that the surface was independently sterilized due to oxidizing agents present in the soil, which also gave it its red tint. The Viking discovered a barren red planet blown by all winds, covered with craters, cold and dead, like the moon.

Some scientists from the team did not agree with this, and argued that the fourth experiment simply did not go well - as it did in experiments on Earth. A group of activists, which included Levin, wrote letters and made speeches, urging NASA to publish the full details of the project. In 2016, during the celebration of the 40th anniversary of the mission at NASA, he repeated these requirements. He predicted that Curiosity would find complex organics on Mars. When he saw how Curiosity recorded methane emissions, he noticed that methane disappeared too quickly to be explained only by ultraviolet radiation: "This disappearance could be due to methanotrophs using methane for their small, ideal life cycle."

Other Martian probes gave controversial results. "Opportunity "and" Spirit ", launched in the early 2000s, reports of which have excited millions of fans around the world, including myself, have been designed and developed by geologists and engineers, not biologists. Water Evidence extracted lander" Phoenix " in 2008, his camera captured clearly visible drops of water on his cold steel legs. The results of the simulations indicated that either the water was condensed on the grains of calcium perchlorate carried by the wind., a salt mineral, the properties of which allow it to extract water from the atmosphere, or a landing mixed up dirty ice beneath the surface, as a result of which its grains appeared on the legs, which melted and turned into drops. But the point is that, as the scientist who participated in this project, Nilton Renno from the University of Michigan said: “Everywhere on Earth, where there is liquid water, there is microbial life”.

Paradoxically, the Earth is one of the best places to search for promising areas of Mars. On the frozen plains of Antarctica, you can find areas like small stones that are similar to Mars. About 5 kg of Martian stones fall on the Earth every year. If a large meteorite hits Mars, it sends stones into space, at a speed that overcomes the planet’s small gravity. The gravity of the nearest neighbor, our planet, catches some of these stones. They fall to the surface of the Earth and are easiest to find in lifeless, ice-covered regions, such as the Antarctic. The authenticity of the stones is confirmed by chemical analysis of the molten glass-like substance appearing on the stone due to heat. If this substance contains exactly the same mixture of gases,

Tiny pieces of the famous Martian meteorite discovered in Antarctica, ALH 84001In 1996, NASA researcher Dave McKay and his team announced the discovery of fossilized microbes. Today, most scientists agree that this is unlikely. But many years ago there was obviously a lot of water on Mars that made up the oceans and rivers. Its mineralized traces are visible all over the planet - floodplains, alluvial basins, branches of long-dried rivers. In 1887, astronomer Luigi Schiaparelli called the rift valleys canali visible in early telescopes, which in Italian means “channels” (although English-speaking researchers incorrectly translated this word as “channels”). At the beginning of the 20th century in Arizona, Percival Lowell decided that he saw the activity of the Martian rivers and seasonal changes in vegetation. In fact, several Martian probes recorded the presence of morning haze in the Martian canyons.John Carter , who forced several generations of young Americans to go in search of adventure. However, what Lowell encountered in his observations was simply due to the flaws of the mirrors. And Burroughs, divorcing his wife because of a Hollywood actress, came across a gold mine of public credulity.

In 2010, a student at the University of Arizona studying a spacecraft in Mars orbit MRO noticed intermittent dark stripes descending from the ridges in parallel - they appeared and then disappeared, reminding seasonal changes. What Luyendra Ojha saw was taken by an experiment that took HiRISE high-resolution photos.. Images of dark streams could be found in dozens of places. Oyha was very interested in this, and he compared the observations of HiRISE with the mineral maps of Mars. Observations of the spectrometer showed the presence of salt solutions in several places - but only when dark stripes appeared and expanded. Using MRO spectrometers, Oyha with the team analyzed the reflection of these light strips, and found traces of sodium and magnesium perchlorate there. It turned out that the water of Mars contains natural salt antifreeze.

Imagine a cold planet, which is then filled with water, then dries up, and on which is located the largest volcano in the solar system. Giant lakes contain as much water as in the Arctic Ocean, and they are fed by rivers that place alluvial deposits in their deltas. That was the young Mars. Now imagine a sulfur-smelling, acidic, ocean-covered planet with a toxic atmosphere and hot greenhouse gases, in the absence of oxygen and protecting against the radiation of ozone, which was constantly thrown into comets, and then dolbanuli planet the size of Mars, because of which it was knocked out enough rocky rock to form a satellite that stretched the surface of the planet in high tides with a skyscraper. Welcome to the young Earth.

For this and other reasons, NASA researcher Steven Benner and other scientists have suggested that life originated on Mars, and then brought it to Earth through fragments thrown into space. Looking through the Viking work reports in the Houston library, Benner, in a 40-year-old report, found precious clues to the mysteries they had seen on hot nights. He described it as a “mass delusion.” Studying the DNA of ancient microbes, recreating their genes and proteins, Benner tried to combine the origin of life on Earth with the existence of life in the solar system. In several of his works, he points out that Mars had "high temperatures and a cycle of humidity and dryness," which allowed the building blocks of RNA to concentrate and create "the chemistry we need."

The problem was that many previous statements about the existence of life and water on Mars were completely wrong. But many ancient microbes flourished in a similar environment of ice and alkali on Earth. Therefore, researchers rushed to explore the sulfur caves, hot springs in Kamchatka containing molybdenum and borate, Yellowstone National Park and salt lakes of the Antarctic. And they found something quite interesting.

Chris McKay and Penelope Boston from NASA have been looking for the most remote and extreme places on Earth, where signs of metabolism and microbial origin are present. Boston used to be a professor at the Institute of Mining and Technology in New Mexico, and her parents are circus coaches. She began by studying the microbes in the Arctic, and then went on to search for life in deep caves. Alison Murray from California was looking for extreme microbes in the Antarctic. Suddenly, after launching Curiosity, everyone became interested in what could survive in an ice-covered lake or plain, or in a remote cave or mine a few kilometers below the surface of the planet. From their point of view, the likelihood of microbial life on Mars, which Boston estimated at 30%, began to rise. If tiny life forms can exist in the hostile conditions of a lake,

Starting as director of the cave and karst research program at the institute and taking part in founding the National Cave and Karst Research Institute in New Mexico, Boston campaigned for Mars exploration, helped create the Mars Underground documentary , and organized several discussions she managed to convince the skeptics of NASA, proving a greater likelihood of life on Mars. She was so successful that in 2016, NASA appointed her the new director of her Institute for Astrobiology in Moffet Field, California, giving her an interesting opportunity to “direct your favorite science at the highest level,” she told me.



After Nevada, biochemist Alison Murray from the Institute for Desert Research joined geophysics Peter Doran from the University of Louisiana to study microbes and ancient climates in salt, ice-covered lakes of the Antarctic, and together they discovered a wide range of bacteria and archaea . “They do little — they spend most of their time hibernating,” said Murray, who drilled ice cores in the Antarctic Vida lake, “but they are there.” In the depths of the sea water was warmer, but the cores allowed to raise the ice from the very bottom.

New ideas sent researchers to the west of the United States, where Gill Banfield, a biologist from Berkeley, studied the Colorado River and water in an abandoned Californian mine on Iron Mountain. Banfield discovered several new groups of bacteria in a single shaft containing toxic waste. These strange, hitherto unknown microbes relied in the survival of communities of other organisms. This could explain the fact why so few of these microbes could be grown in the laboratory. Working on a shallow aquifer near the Colorado River, the Banfield team applied a new technology to search for organisms and discovered dozens of new groups of bacteria, which practically revolutionized the tree of life. The Banfield team divided 789 organisms into 35 groups, 28 of which were discovered by them in the realm of bacteria. The sorting was based on the evolutionary history of the organisms and on the similarity in their 16S rRNA gene - bacteria that had 75% similarity turned out to be in the same group. The team in each season and at each level found completely different symbiotic species.

In the fall of 2016, the Banfield team discovered new groups of bacteria in a single aquifer, thus doubling the number of bacteria groups known all over the planet - this serious underground discovery changed the whole tree of life again. Banfield also studied microbial colonies in the intestines of babies, which led her to the newborn care unit. Her work and the work of other scientists in Yellowstone, in the Atacama Desert in Chile, in the abandoned mines of Colorado and California, and even studying the contents of the mouth of dolphins led to a change in the tree of life, published in the journal Nature Microbiology. Over the past 15 years, about a thousand unknown species have been added to it. The second surprise in the discoveries of Banfield was that almost half of the new species of bacteria belonged to the group that was thought to be

And then Nora Noffke provoked the search for life on Mars.

During the whole hot virgin summer Nora Noffke from the University of Old Dominion [Old dominion is the informal name of the piece. Virginia / approx. transl.] studied photos of the Gale crater taken by the Curiosity rover. Noffke was reputed to be the leading expert on microbial-induced sedimentary structures, WMOS (microbially-induced sedimentary structures, MISS ) —that she invented the term she called stone structures left after microbial mats on salt flats. Many people are familiar with stromatolites- fossil remains of ancient microbes, but few understood the importance of tidal microbial mats. Over the 30 years of her career, Noffke traveled to five continents, studying and categorizing more than ten forms of mat, from roll and wavy to wrinkled. Stromatolites like mounds are popular among tourists in the shallows of Australia and Hawaii, as well as in the Caribbean. Noffke found her WMOS in remote parts of Australia. Virtually no one has ever seen them, and now they are considered the oldest evidence of life on our planet.

In the summer of 2014, NASA invited Noffke to speak at a meeting where the landing site for the rover 2020 was chosen. If early Earth and Mars were similar to each other, Noffke said, it is possible that there are microbial deposits on the red planet. This forced one of the students, geochemist Ken Farley from the California Institute of Technology to stand up in the chair. Her team has just published a paper on the structures that “Curiosity” saw in the ancient mud sediments of the plain along which Curiosity made its way 22 km towards Sharpe Mountain . Her heart jumped out of her chest. The images looked very familiar. But she knew about the dangerous tendency to see microbial structures everywhere. "I will publish the work with my hypothesis and see what people say," she decided.

When she published a paper in January 2015 that hinted at signs of microbial life on Mars, the response from the Curiosity team was pretty tough. Noffke was accused of imparting wishful thinking. The team even created a special site that refutes her claims.

The 2014 methane spike could be attributed to pollution caused by Curiosity itself. But methane is also a characteristic sign of the vital activity of microbes, such as archaea. And then it became known observation from 2015, made by MRO - he saw the salt water flowing along the slopes of the crater Gail at temperatures below freezing; water was not allowed to freeze perchlorates.

Passions ran high. The Curiosity team admitted to messing up with geology. Noffke responded to their statement. “Now it’s an eroded hillside, but before that it was a lake that was in a completely different environment. They say it is a multi-channel river. But this is absolutely not the case. This is a slope left over from a winding river. It is in such places on Earth that there are microbial mats - right in such! ”

The only way to solve this question was to send people to Mars. The problem with this is to bring so much fuel with you to make it enough to detach from the Martian surface and return to Earth. Therefore, the first stage is likely to be sending people into orbit around Mars - this proposal was made by the Planetary Societywhose chairman is Bill Nye . In the more distant plans, NASA has sent people to Mars in the 2030s, before which the European-Russian mission Exomars 2020 will choose the bottom of a dried-up lake suitable for landing.

Other evidence of the ancient activity of microbes in the Gale crater basin was obtained by the University of Oregon, where geologist Greg Retallak noted a high content of sulfates in the soil, which can only be explained by the work of anaerobic bacteria in an oxygen-free environment. Some of the “vesicular structures,” or bubbles seen in photos from “Curiosity,” resemble those produced by microbes on Earth after rain, as Retallak wrote in the journal Geology. Noffke's senses were hurt by big science and public enthusiasm for extraterrestrial life. Her work was merely a description of the hypothesis, not a full statement, and the hostility of the Curiosity team took her by surprise. However, the team sketched a new course, returning the rover back to the place where methane was detected, and in the same season when they were first discovered. And this,

Therefore, researchers and fans watched with impatience as the probe of the European space agency Sciaparelli went into orbit around Mars in the fall of 2016, prepared for the descent of the rover. The test descent vehicle, controlled by the parent module from orbit, descended in the area of the Meridian Plateau on October 19, 2016. As planned, the parachute opened at 12 km and the heat shield at 7.8 km. And then there was an inertial measurement error, which went a second more than necessary, and because of the large data flow, the system produced a calculated height that was below the surface level. A one-second error caused the second parachute to open, and the brake motors would turn on too early, due to which the rover made a hard landing and fell apart. Its fragments can be observed with MRO.

This test was a cruel disappointment, but it was just a test. The European Space Agency plans to return to Mars in 2020.