Throughout the past forty years, with twelve years as the director of NASA's planetary science division and the last three as its chief scientist, he has significantly influenced NASA's scientific research by overseeing missions throughout the solar system and contributing to over 100 scientific papers on various topics. While focusing on Earth's magnetic field and plasma waves early in his career, he later expanded his research interests. One of his recent notable proposals is the "confidence of life detection," or CoLD, scale for verifying the detection of alien life. He has also suggested the possibility of terraforming Mars to make it habitable for humans by using a large magnetic shield to protect the planet's atmosphere. Additionally, he has supported the exploration of other worlds, including a mission to Jupiter's icy moon, Europa, set to launch in 2024. Before a December conference of the American Geophysical Union in New Orleans, Green discussed various aspects of his work and the quest for life within our solar system. The following are edited and condensed portions from our interview where he discusses the importance of a systematic approach to the search for life using the CoLD scale, which ranks potential discoveries from one to seven. In response to a question about the need for such a scale, Green referenced the recent observation of phosphine in the atmosphere of Venus by scientists a few years ago. The size of what they saw made them think that life was a significant possibility. On the CoLD scale, where seven indicates the discovery of life, it only ranked as a one. It didn't even reach a two. They later realized that there was contamination in their signal and it may not actually be phosphine, and they are unable to reproduce it. Therefore, there is a need for better communication. Methane is commonly found on Mars. While 95% of methane on Earth is linked to life, there is a small percentage that is not. We are currently at CoLD Level 3, but if a scientist presented an instrument that could upgrade us to CoLD Level 4, I would immediately fund that mission. It is important to take the right steps towards finding life in the solar system, rather than making drastic jumps. NASA has been focused on the search for life on Mars since 1976, but it is not surprising that we have not yet found life. A: Our current approach is more systematic and intelligent in identifying the signs of life that can develop over time. Earth, at 4.5 billion years old, is now teeming with life. However, if we look back a billion years, we would see that Venus was once a blue planet with a substantial ocean. It is possible that Mars had life in the past when it was a blue planet billions of years ago before losing its magnetic field and water. Despite landing the Viking landers in a less than ideal location on Mars, scientists would have liked to discover signs of life on the planet's surface. It felt as if we were placing something in the Gobi Desert instead of where we should have, in Jezero Crater, the river delta where the Perseverance rover is currently located. Back then, we were unaware of its existence. One of the Viking experiments suggested the presence of microbial life in the soil, but only one of the three instruments confirmed it, so we couldn't confirm the discovery of life. With the upcoming sample return mission, we will have conclusive evidence. We didn't anticipate the need for a sample return mission. Question: In the past, you mentioned the idea of terraforming Mars by using a large magnetic shield to prevent the sun from stripping its atmosphere, thus allowing the planet to retain more heat and become habitable. Is this idea feasible?
Answer: Yes, it is feasible. By stopping the atmosphere from being stripped away, the pressure on Mars will increase, leading to the planet naturally beginning to terraform itself. We desire for the planet to contribute in any way possible. As pressure increases, so does temperature. The initial stage of terraforming occurs at 60 millibars, which is ten times our current level. This point is known as the Armstrong limit, where human blood would not boil if exposed to the surface. Without the need for a spacesuit, there would be greater freedom of movement. The increased temperature and pressure create conditions that allow for the cultivation of plants in the soil. Various methods for creating a magnetic shield are being considered. I am currently in the process of finalizing a paper that I have been working on for two years, although I anticipate it will not be well received. The planetary community is generally opposed to the concept of terraforming. I believe we have the ability to alter Venus by using a physical shield that reflects light, which would lower the temperature. NASA approved the Europa Clipper mission in 2015 to search for signs of life on Jupiter's moon Europa, following the detection of plumes erupting from its subsurface ocean in 2013. Would you have preferred for this mission to happen sooner? Text = A: I would have liked to see it earlier, but it was not possible. Some missions are so large that they are called strategic missions. To make them happen, everything has to line up perfectly. You need to propose it, have a strong case, present it to NASA administrators, and then pitch it to Congress. I proposed a Europa mission every year. Each year, the administration showed no interest in visiting Europa, but the discovery of plumes on the moon led to the Europa mission. At a 2013 American Geophysical Union meeting, scientists discussed finding a plume on Europa using Hubble, prompting excitement and plans for a press conference. I dialed NASA headquarters again, and they successfully completed the task. I brought that information back to headquarters and incorporated it into the narrative of Europa. This was a game-changer. They expressed interest in pursuing the idea. When asked about Congress's decision not to include a lander in the mission, did you support that decision? A: Although I would like to have a lander, it is not currently part of the plan. Having a lander would complicate the mission, but everything we are doing on Clipper is preparing us for a potential future lander mission. I made sure that we have a high-resolution imager so that when we fly over certain areas, we can gather the information needed to safely choose a landing spot. Europa's terrain is hazardous, so without high-resolution imaging, landing would be impossible. It's important to take small steps rather than a big leap, as failure is more likely with the latter approach. Viking serves as an example of when we took a significant leap without enough knowledge. We lacked information about the soils, toxins, and water on the planet before sending the two Vikings to the surface. There were 10 crucial things we should have known beforehand. Despite retirement, the individual plans to continue working on scientific papers. Paraphrased text = A: Yes, definitely. I am currently working on a paper about Mars, a paper about Europa, and a book on astrobiology. I have a strong passion for science. Copyright 2022 by The New York Times Company.