Is there life on Mars? Can Mars 2020 reveal the truth of an experiment conducted half a century ago?

Late July to early August 2020 is the "launch window" for Mars exploration. The UAE's Hope has taken the lead, and China's Tianwen-1 and the US Perseverance will follow closely. One of the scientific goals of the US "Mars 2020 Mission" is to determine whether there is life on Mars. Decades ago, the biomarker experiment of NASA's "Viking Mission" concluded that there is life. Although the official report stated that it did not provide clear evidence, there are still scientists who have not given up the hypothesis of life on Mars, and some have even put forward an astonishing hypothesis - "Mars mushrooms". Who is right and who is wrong? Perhaps Perseverance's exploration journey will give us the answer.

Written by | Xiaoye

The fate of the Earth in 2020 was full of misfortunes, but the disasters did not stop humans from exploring space. On July 20, the UAE's Hope took the lead in setting off, and China's Tianwen-1 and the United States' Perseverance will soon follow, carrying the beautiful expectations of human scientists to the red planet 55 million kilometers away.

Investigating traces of life on Mars is one of the important scientific research tasks of this exploration. Although there are no "Martians" on Mars, whether there are low-level or primitive life forms and whether they can provide ideas for explaining the origin of life have always been questions that scientists have been pursuing. In the history of Martian life exploration, the National Aeronautics and Space Administration (NASA) has the most experience, and they have not given a particularly clear statement before. However, some scientists have always insisted on saying yes.

It all started with the Viking missions half a century ago. Since the 1960s, NASA has set its sights on this popular "God of War" planet. From the flybys of Mariner 4 in 1964, Mariner VI and VII in 1969, to the orbital missions of Mariner 9 in 1971 and 1972, NASA has been cautious and has always insisted on in-depth exploration of Mars. In fact, in the late stage of the "space race", one of NASA's next goals was to land astronauts on Mars.

In 1975, NASA officially launched the "Viking Mission". Just like in the Middle Ages, the ambitious Vikings set sail from the Scandinavian Peninsula, and with amazing courage and perseverance, they traveled across the European continent and the vast Arctic, creating the "Viking Age". The two Viking exploration spacecrafts carried the ambitions of the earthlings to explore the "God of War". In addition to understanding the climate and geological properties of Mars, another goal was to find traces of life.

In the summer of that year, two spacecraft headed for Mars one after another. After a year of flight, the Viking 1 lander first landed on the western slope of Chryse Planitia on Mars on July 20, 1976, and the Viking 2 landed on Utopia Planitia 4,000 miles away on September 3.

The name "Viking" seems to have endowed this mission with an unparalleled tenacious "Viking spirit". The original plan was for a 90-day exploration mission, but the service life of the orbiter and lander far exceeded the design expectations. In particular, the Viking 1 orbiter worked "diligently" in the orbit of Mars for four years. As the gas fuel gradually ran out, the entire exploration mission officially came to an end on May 21, 1983.

The Viking lander consists of five basic parts: the lander body; the biological shield and base; the fuselage; the bottom cover and parachute system; and the lander subsystem. The instruments carried are used for the main scientific research purposes of the lander: biological research, chemical composition analysis (organic and inorganic), meteorology, seismology, geomagnetism, and geomorphology, Martian surface and atmospheric physics. 丨Image source: NASA

During the mission, the scientific instruments on the lander obtained more data than expected. The biological experiments carried out included the Climate Mass Spectrometry Experiment (GCMS), the Gas Exchange Experiment (GEX), the Labeled Release Experiment (LR) and the Pyrolysis Release Experiment (PR). In addition, many high-quality photos were taken during the Viking mission, including 4,500 photos taken by the lander and 52,000 photos taken by the orbiter. The photos provided by the lander allowed people on Earth to see the desolate surface of Mars up close for the first time.

The first color photo of the Martian surface taken by the Viking 1 lander | Source: NASA/JPL

Among the four major biological experiments mentioned above, biologists have high hopes for the Labeled Release (LR) experiment. The specific experimental process is not complicated. The Viking 1 and 2 landers collect Martian soil samples, then inject a drop of diluted nutrient solution into the sample, and then detect whether metabolic byproducts appear in the air above the soil. Before injection, the nutrients have been labeled with radioactive carbon 14. If the microorganisms present in the soil metabolize the nutrients, they should release radioactive byproducts, such as labeled carbon dioxide or methane.

Before launching the Viking spacecraft, the researchers tested the protocol in different terrestrial soils in extreme environments around the planet, from Death Valley to Antarctica. Every time, the results were positive. At the same time, the researchers also conducted control experiments one by one, heating the samples to a high temperature of 160°C to kill all life forms, and then repeated the experimental operation, and every time the results were negative. To confirm that the experimental process would not produce false positive results, the researchers also used known sterile soil samples, such as rock samples from the moon and soil samples from the volcanic island of Sartsi near Iceland, which ultimately produced the expected negative results.

The researchers were confidently looking forward to the results of the experiments on Mars by Viking 1 and 2. However, what they did not expect was that this experiment would become the most controversial Mars experiment in history, and NASA kept silent about it for nearly 50 years.

From the most promising experiment to the most controversial experiment The lead researcher of the LR experiment is Dr. Gilbert Levin. Gibert Levin has a rich life experience. He served in the US Navy during World War II, worked as a public health engineer at the Maryland Department of Health, and founded his own biotechnology company Biospherics Research Inc. (now Aikido Pharma Inc.). In 1963, he received a Ph.D. in environmental engineering from the School of Engineering at Johns Hopkins University. He has obtained many patents for his inventions, especially his innovative methods for detecting microorganisms, which attracted the attention of NASA. Therefore, the latter signed a series of contracts with him in the early 1970s and invited him to develop extraterrestrial life detection experimental programs suitable for space missions.

Gilbert Levin's colleague Patricia Ann Straat also came from Johns Hopkins University. Straat was an assistant professor at Hopkins, studying molecular biology and enzyme systems. Straat watched the 1969 moon landing on TV and longed to participate in NASA's grand space exploration program. At that time, the experiment designed by Levin was selected by NASA and became one of the biological experiments of the "Viking Mission". After a discussion between the two like-minded scientists, Straat was deeply attracted by the LR experiment and immediately joined the team.

She still can't forget the scene of watching the Viking landing with the whole team at the JPL laboratory in California. "Half of the people present thought the lander might crash, but suddenly a loud voice came: 'We landed safely', and everyone was so happy." She recalled. The final result of the LR experiment made the two even more excited.

In a paper published in Science magazine in 1976, Gilbert Levin and Patricia Ann Straat reported in detail all the results of the Mars life detection experiment. The paper mentioned that after adding nutrients containing radioactive carbon 14 to the Martian samples, soil tests at two landing sites 4,000 miles apart detected similar radioactive gas releases. In order to rule out false positive results that may be caused by the strong ultraviolet radiation on Mars, the lander also specifically selected soil samples buried under rocks, which also obtained positive results. The "active" response in the soil was stable at 18°C, and the activity weakened when the temperature was raised to 50°C after heating for 3 hours, while the sterile Martian soil sample at 160°C showed a negative result as a control group.

However, in addition to the LR experiment, other experiments at the same time, such as gas chromatography-mass spectrometry experiments, did not find any traces of organic chemistry near the landing site - and the controversy began. NASA's final official report stated: "The soil near the landing site did not provide clear evidence of the presence of living microorganisms." Moreover, scientists in NASA's own laboratories were unable to replicate Levin's LR experiment results.

In addition, according to NASA, Mars has a self-sterilizing function. Biologists participating in the mission believe that the solar ultraviolet radiation that fills the surface of Mars, coupled with the extremely dry soil and the oxidizing properties of the soil chemistry, will prevent the formation of living organisms in the Martian soil. Therefore, it is still controversial to conclude that life exists on Mars.

NASA believes that the simulated life activities found in the LR experiment may be unknown chemical reactions. Levin and Straat also believed that the LR results might not be clear, so they stated at the end of the report: "There is currently no chemical experiment that can quantitatively replicate the LR Mars data. Despite the existence of (non-biological) hypothetical theories, the most reasonable possibility is that we have observed life activities on Mars."

In the following decades, as NASA launched more Mars exploration missions and used more advanced technologies, scientists gained a clearer understanding of the planet, discovering liquid water, methane, etc. In particular, in 2014, Curiosity not only detected high concentrations of methane in the atmosphere, but also confirmed for the first time that Martian rock powder contained organic molecules such as organic carbon, which can be said to be one of the most important discoveries of NASA's Mars exploration in half a century. At the same time, this result also made Levin more determined to stick to the LR experimental results of that year.

In fact, since 1997, Levin has been revisiting the past and frequently speaking out in public to support the conclusions of the microbial activity in the LR experiment. In 2016, Levin and Straat jointly published an opinion article in the journal Astrobiology. Based on new discoveries on Mars in recent years and the idea that inorganic substances mimic metabolic activities, they re-examined the LR experiment of the 1970s and believed that non-biological substances could not fully explain the results of the LR experiment, and the best explanation was Martian microorganisms.

The results of the Viking 1 injection experiment show that after the first injection, the soil sample showed strong radioactive red (, indicating metabolic activity inside), while the control soil sample showed no reaction (blue) | Source: Levin and Straat, 1977, Biosystems. ©Elsevier

In an interview with the media, Levin said: "Since I first firmly proposed that the LR experiment detected life in 1997, most review journals have rejected our article submissions. Straat and I submit papers to the International Society for Optical Engineering (SPIE, which includes the field of astronomy) every year, but most of them are ignored by astrobiologists." He can only put these articles on his personal website.

Straat, a staunch supporter, was interviewed by Scientific American in 2019. She said that she did not completely agree with Levin's views at first, but as NASA found more and more evidence on Mars, she began to think that they did find microbial life. "Some complex organic molecules have been found on Mars, but no simple organic molecules similar to those required for life, such as alanine and glycine, have been found," she said. She is looking forward to future Mars exploration experiments, hoping to eventually confirm or refute their experimental findings.

In this regard, Luther Beegle, a planetary scientist at NASA's JPL laboratory, believes that the truth is actually very simple: the Viking project did not find life on Mars. "They did a lot of experiments and got a lot of results that they couldn't understand." Given that NASA's understanding of Martian soil and atmosphere was very limited at the time, he said that they should have started with geological and chemical experiments instead of jumping right to biological metabolic activity detection experiments. The LR experimental results were actually very ambiguous.

Stranger said: Are there mushrooms growing on Mars? In the history of Mars exploration, official agencies and scientists have always been the main force, but NASA will publish the photos they took, which gives some other researchers the opportunity to study.

On January 27, 2015, NASA released a color photo on its official website taken by the Mars rover Opportunity in 2004 near Eagle Crater. The photo shows round objects emerging from the surface of Mars with a gray-blue glow. The official nickname for them is "Mars Blueberries", which are actually mineral stones rich in hematite, proving that there was an ancient water environment in this area of ​​Mars.

Color photos of "Mars Blueberries" displayed on NASA's official website | Image source: https://mars.nasa.gov/resources/6944/martian-blueberries/

However, some scientists do not agree with this official statement. At least Dr. Rhawn Gabriel Joseph has other guesses - he believes that Martian blueberries are actually mushrooms.

The name Rhawn Gabriel Joseph will attract the attention of the scientific community this year, first because of the "Mars blueberry" photo above, and secondly because of the involvement of the magazine "Astrophysics and Space Science" under the well-known publisher Springer. What connects the two is Dr. Joseph's latest paper in 2020, which cited hundreds of photos taken by Opportunity in Eagle Crater on Mars and criticized NASA's hematite claim. He believes that the environment of Eagle Crater cannot produce spherical hematite minerals, and puts forward his own hypothesis: mushrooms, algae, fungi and other related organisms may have already settled on the red planet, and may have participated in the photosynthesis and oxygen production process on Mars.

He and his team analyzed 185 photos taken by Opportunity over 36 Martian days, magnified them 300 percent, and identified them with the naked eye. He said: "These mushroom-like species have stalks and bulbous caps, attached to the surrounding rocks by thin stems. How come no one saw them?"

According to his article, the Mars rover took thousands of photos of such Martian mushroom species, all of which were fixed at an upward angle, as if participating in photosynthesis on Mars. The orientation in each photo changed. As for where these Martian mushrooms came from, Joseph also gave his own opinion: it was the solar wind that sent mushroom species from Earth to Mars, and billions of years ago, our planet had already sowed the seeds of life on Mars and other planets in the solar system...

No matter how amazing the content of the paper is, the paper was accepted by the journal Astrophysics and Space Science and entered the peer review stage. Joseph once revealed to the media that his article was originally scheduled to be published online on April 10 this year, and then postponed to April 16. But on April 20, the journal announced that because the author refused further peer review, he eventually withdrew his manuscript. Subsequently, Joseph uploaded the paper on researchgate.net, hoping that everyone would read it. This is a nearly 40-page paper with 180 references. Obviously, he is not joking.

Who is this Dr. Joseph? When you type his full name into Google, the first thing that comes up is his website with a very strong personal style. In addition to a list of publications and reviews, there is also a personal autobiography: I have been versatile since I was a child, and I love music, art, painting, books, nature, and girls... After telling about his strange personal experiences, he suddenly changed the subject and introduced his personal scientific research and academic career, "I was born for science." However, he did not give any specific education and work background.

According to him, he has been engaged in neuroscience research since the 1970s. His main achievements include neuroplasticity and primate brain function recovery, the hormonal basis of gender differences, the impact of the environment on the neuro-synaptic connection of the primate brain, and so on. After entering the new century, his scientific research direction has also entered a new era. With one hand in hand, he holds the small primate brain and the other hand reaches out to the vast space biology. He supports Panspermia (Panspermia, which is simply a conjecture that life forms exist everywhere in the universe and spread and reproduce everywhere with the help of asteroids and meteors.) He studied the origin of life in the universe. Therefore, the topic of life on Mars is naturally included in the bag. In fact, in 2019, his contribution to "Astrophysics and Space Science" published his research on life on Venus - mushrooms also grew on it.

In 2009, he founded the Journal of Cosmology, a private academic journal. It is reported that the editorial board is composed of professionals and all publications are peer-reviewed. He has also published many articles on it, making many comments on Martian mushrooms, fungi, and bacterial contamination, criticizing NASA for not sterilizing the Mars rover, and supporting the Viking LR experiment mentioned above.

For all of the above, coupled with the large number of Mars exploration projects launched this year, he has received some media attention. Inverse magazine contacted NASA for consultation on whether Joseph's views are reliable. NASA's public relations specialist made it clear that NASA does not comment on anyone's research casually, but relies on the scientific community and peer review process to evaluate scientific significance. NASA officially replied that "the general consensus in the scientific community is that the current conditions on the surface of Mars are not suitable for the existence of liquid water or complex life." And "non-mainstream" scientists like Joseph believe that this is a conspiracy theory-there are higher-level forces trying to cover up the existence of extraterrestrial life. However, even for serious astrobiology research, wild theories can only wait for technological development, and now it seems that the time has come.

Gazing at Mars and exploring traces of life Whether there is life on Mars, this Mars exploration project may provide the answer. In addition to China's Tianwen and the UAE's Hope, the United States' Mars 2020 is highly anticipated.

The landing site of the "Perseverance" Mars rover was chosen to be the 3.5 billion-year-old Jezero Crater. It is now barren, dry and cold. However, scientists believe that billions of years ago, Mars had a thick atmosphere and the planet was once extremely warm. Water flowed freely and gathered in craters like Jezero to form lakes. Such favorable conditions are likely to promote the birth of life.

Image of Jezero Crater | Source: NASA/JPL

One of the scientific missions of "Perseverance" is to collect Martian rock and soil samples, look for traces of life, and solve the mysteries of Mars. According to the plan, the journey to Mars will start from the dark surface of the crater, and then walk along the fine-grained clay layer on the edge of the delta, where an ancient river once flowed into the lake. On Earth, such lake mouths often find traces of life, and Perseverance will look for organic compounds in Martian rivers that reveal the existence of microorganisms in the past. After that, the rover will continue to move forward, passing through a hard sandy area where the soil particles may have been formed for billions of years, and there have been rivers from the oldest areas of Mars and flowing downward. The next stage after this is the shore of the ancient carbonate-rich lake. These limestone-like carbonate layers are called stromatolites on Earth. Stromatolites on Earth are formed by bacterial growth and can be described as geological "capsules" that condense the history of life development.

The exterior design of the Mars rover is largely inspired by its predecessor, Curiosity, but the interior is equipped with a brand-new sample acquisition system. This complex mechanical system can drill holes, transport, image and store samples on the Martian surface, such as chalk composed of rocks and soil. The Mars rover will make at least 30 such cores, which will be packaged and sent back to Earth for further analysis in future projects. Perseverance is equipped with a set of tools that can identify the chemical composition of Martian rocks and soil. This set of tools can image the distribution of organic molecules in rocks, thereby helping scientists distinguish between organic debris from meteorite impacts and the remains of microbial life.

Although we have to wait patiently for a while for the "express delivery" from Mars, the time left for mushrooms may not be long. Since ancient times, people on Earth have never stopped asking about the sky. In 2020, the "window" for exploring Mars has been opened. This time, we are full of courage, curiosity and hope, and we will start our journey of perseverance towards the fiery planet.

References

1. https://mars.nasa.gov/mars-exploration/missions/viking-1-2/

2. https://en.wikipedia.org/wiki/Viking_lander_biological_experiments

3. https://blogs.scientificamerican.com/observations/im-convinced-we-found-evidence-of-life-on-mars-in-the-1970s/

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6. https://www.liebertpub.com/doi/full/10.1089/ast.2015.1464

7. https://www.gillevin.com/

8. https://www.scientificamerican.com/article/looking-for-life-on-mars-viking-experiment-team-member-reflects-on-divisive-findings/

9. https://www.researchgate.net/publication/340610633_Life_on_Mars_Colonies_of_Photosynthesizing_Mushrooms_in_Eagle_Crater_The_Hematite_Hypothesis_Refuted

10. http://brainmind.com/publications.html

11. http://journalofcosmology.com/

12. https://www.inverse.com/science/mushrooms-on-mars-a-wild-story

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14. https://www.cnet.com/features/the-space-tiger-king-and-the-mushrooms-on-mars/#ftag=CAD590a51e

15. https://phys.org/news/2014-12-curiosity-rover-ancient-chemistry-mars.html