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If you are looking for a manual on hunting for extraterrestrial life, you are in luck.
Some of the greatest experts in the field, including a team of UC Riverside researchers, have authored an important series of articles on the past, present and future of the research of the life on other planets. Posted in astrobiology, the documents represent two years of work by the Nexus for Exoplanet Systems Science (NExSS), a research network coordinated by NASA dedicated to the study of global habitability, and by the Institute of Astrobiology of NASA.
Scientists have identified more than 3,500 planets around other stars (called exoplanets) and many more will be discovered in the coming decades. Some of them are rocky planets, the size of the Earth, which are found in the habitable areas of their stars, which means that it is neither too hot nor too cold for liquid water to exist.
The five articles will serve as a reference for scientists looking for signs of life, called biosignatures, in the data they collect from future telescope observations.
"In less than 30 years, we went from not knowing if planets existed outside our solar system to be able to locate potentially habitable planets and collect data that will allow us to search for the signatures of life", said Edward Schwieterman, a postdoctoral researcher in the Department of Earth Sciences UCR and lead author of the first article in the series. "These advances offer unprecedented opportunities to answer the age-old question," are we alone? "But at the same time we are asking for a lot of care in developing robust models that allow us to search and identify life with a high degree of certainty."
The Schwieterman article reviews three types of biosignatures that astrobiologists have previously proposed as markers of life on other planets, all of which must be detected remotely from distant orbital stars exoplanets that we can not not reach in person. Markers include:
- Gas biosignatures: by-products of life that can be detected in the atmosphere, such as oxygen produced by photosynthesis, as on Earth.
- Surface Biosignatures: life-induced changes in the absorption and reflection of light on the surface of a planet, such as the red edge caused when plants absorb red light during photosynthesis, but reflect infrared light that does not Is not used.
- Time biosignatures: time-dependent fluctuations in gaseous or surface biosignatures, such as biologically modulated changes in the Earth's atmosphere that occur during different seasons.
Schwieterman is part of the NASA-funded Alternative Earths Astrobiology Center funded by NASA, an interdisciplinary group that develops a "search engine" for life on other worlds by plunging into the world. dynamic history of our planet, 4.5 billion years. Although radically different in terms of atmospheric composition and climate, the different chapters of Earth's history have one thing in common: oceans that abound with a remarkable diversity of simple and complex life.
"We use the Earth to guide our search for life on other planets, because that is the only example we know," said Timothy Lyons, a prominent biogeochemistry professor and director of the Center for Biogeochemistry. astrobiology of alternative lands. "But the Earth actually offers us a great diversity of possibilities: instead of being restricted to a study of current life, we use geological and geochemical analyzes to examine the billions of years of life, of Evolution and prosperity on Earth are very different today, hence the concept of "alternative lands". "
Schwieterman's review describes the complexities of finding life on planets that are too far to visit, including phenomena called false positives and false negatives. "The search for biosignatures is not as simple as looking for a single molecule or compound: atmospheric oxygen, for example, could be a sign of life, but there are many non-biological ways to produce oxygen on an exoplanet., it is possible that life can exist in the absence of oxygen gas, similar to life on Earth or parts of oceans today. "," Said Schwieterman. "This is one of the reasons why temporal biosignatures, which are based on dynamic phenomena such as atmospheric seasonality, could be stronger biosignatures under certain circumstances."
More research on the ways in which nature can deceive scientists into thinking that a dead planet is alive or vice versa is described in the second article in the series. The third and fourth articles propose new research that extends our concept of biosignatures to a myriad of habitable planets radically different from the past or present Earth. The last article discusses how the search for life through biosignatures is incorporated into telescope and mission design.
In addition to Schwieterman and Lyons, Stephanie Olson, a graduate student in Earth Sciences, contributed to this research. The team, along with Christopher Reinhard, an assistant professor at the Georgia Institute of Technology and a member of the UCR-led Alternative Land Astrobiology team, contributed to several other articles in the field. series.
"Together, these documents highlight UCR's contributions to understanding exoplanet biosignatures and implications for future instrument design," said Schwieterman.
"These contributions will provide an entry point for people from disparate fields interested in how they too could contribute to the search for life outside our solar system."
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