June 25, 2018
Researchers at the University of Washington-led virtual planetary laboratory are central to a group of papers published by NASA researchers in the journal Astrobiology, which describes the story ̵
Research efforts are coordinated by NASA's Nexus for Exoplanet Systems Science, or NExSS, a worldwide network aimed at finding new ways to study the old question: "Are We Alone?"
A theme through the research and the discussions behind it the need to consider planets in an integrated way, with multiple disciplines and perspectives.
"For life to be detective of a distant world, it must strongly modify its planet in a way we can detect," said UW astronomy professor Victoria Meadows, leading author of a paper and principal investigator of Virtual Planet Laboratory or VPL for short. "But in order for us to recognize life correctly, we must also understand the planet and the star. The environmental context is important."
The NExSS researchers work will help identify the measurements and instruments needed to search for life using future NASA flagship missions. The detection of atmospheric signatures of some potentially habitable planets may come before 2030, even if the planet is truly habitable or has life will require more in-depth study.
The theses are the result of two years of effort of some of the world's leading researchers in astrobiology, planet science, yor science, heliophysics, astrophysics, chemistry and biology, including several from UW and Virtual Planet Laboratory or VPL. The coordinated work was born by online meetings and a personal workshop held in Seattle in July 2016.
The pace of exoplanet findings has been rapid, with over 3,700 detected since 1992. NASA formed the international NExSS network to focus a variety of disciplines for to understand how we can characterize and eventually search for signs of life, called biosignatures, on exoplanets.
The NExSS network has further developed the area for exoplanet biosignatures and "promoted communication between researchers seeking signs of life on the solar system bodies with those looking for signs of life on exoplanets," said Niki Parenteau, an astrobiologist and microbiologist at NASA's Ames Research Center , Moffett Field, California, and a VPL team member. "This has enabled sharing of" lessons "of both societies."
The first of the articles shows the type of signatures that astrobiologists have suggested as ways to identify life on an exoplanet. Scientists plan to look for two major types of signals: One is in the form of gases that produce life, such as oxygen produced from plants or photosynthetic microbes. The other can come from the light reflected by life itself, like the color of leaves or pigments.
Such signatures can be seen on Earth from orbit and astronomers study constructions of telescope concepts that can detect them on planets around nearby stars. Meadows is co-author, and principal author is Edward Schwieterman, a VPL team member who earned his doctorate in Astronomy and Astrobiology from UW and is now a postdoctoral researcher at the University of California, Riverside.
Ängar is the leader of the second review document, which discusses new research on "false positive" and "false negative" for biosignatures, or how nature can "fool" scientists to think of a planet without living or vice versa.
In this document, Meadows and co-authors review ways that a planet could make oxygen abiotic, or without the presence of life, and how planets of life may not have the signature of oxygen that is abundant on today's earth.
paper's purpose, Meadows said, was to discuss these changes in our understanding of biosignatures and propose a "more comprehensive" treatment. She said, "There are a lot of things in the universe that can potentially put two oxygen atoms together, not just photosynthesis – let's figure out what they are. Under what conditions are they more likely to happen, and how can we avoid being tricked ? "
Schwieterman is co-author of this paper, as well as doctoral students UL Jacob Lustig-Yaeger, Russell Deitrick and Andrew Lincowski.
With such an advance, researchers are now better prepared to distinguish between false positive results from planets that truly host life.
Two documents show how researchers attempt to formalize the lessons learned from the earth and extend them to the vast array of worlds we have not yet discovered.
David Catling, UW Professor of Earth and Space Sciences, is the author of a paper proposing a framework for the assessment of exoplanet biosignatures, given the variables such as the chemicals in the planet's atmosphere, the presence of oceans and continents and the global climate. Doctoral student Joshua Krissansen-Totton is co-authors.
By combining all this information systematically, researchers can analyze whether data from a planet can be better explained statistically through the presence or absence of life.
"If future data from an exoplanet might suggest life, what method can distinguish whether life's existence is close to safety or if the planet is really dead like a doorstep?" Sa Catling. "Basically, NASA asked us to elaborate on how to assign a probability to the existence of exoplanet life, such as a 10, 50 or 90 percent chance. Our paper presents a general method for doing this."
The data as astronomers collecting on exoplanets will be sparse. They will not get samples from these distant worlds, and in many cases will study the planet as a single point of light. By analyzing these fingerprints of atmospheric gases and surfaces embedded in that light, they will distinguish as much as possible about the properties of the exoplanet.
"" Since life, planet and parent star change over time together, a biosignature is no longer a single goal but a series of system features, says Nancy Kiang, biometeologist at NASA's Goddard Institute for Space Studies in New York and a VPL team member. She said that more biologists and geologists will need to interpret observations "where life processes will be adapted to the particular environmental concept."
The final article discusses the field-based and space-based telescopes that astronomers will use to search for life beyond the solar system. This includes a series of observatories, from those in operation today to those that will be built for decades in the future.
In summary, this cluster of papers explains how the exoplanet community will evolve from their current estimates of sizes and pathways of these distant worlds, to thoroughly analyze their chemical composition and so s probably if they end up in life.
"I'm excited to see how this research is developing in the coming decades," said Shawn Domagal-Goldman, an astrobiologist at NASA's Goddard Space Flight Center, Greenbelt, Maryland and a VPL team member. He is also co-author of four out of five papers.
"NExSS has created a varied network of researchers. This network will enable society to carefully evaluate planets for biosignatures than would otherwise have been possible."
NExSS is a multidisciplinary, cross-cutting NASA network for research cooperation.
Tag: David Catling • Edward Schwieterman • Joshua Krissansen-Totton • NExSS • Exoplanet Systems Science Nexus • Russell Deitrick • Victoria Meadows