Astrobiology

Using Earth’s history to inform the search for life on exoplanets

Anonymous — Tue, 08 Dec 2020 16:26:50 +0000

Using Earth’s history to inform the search for life on exoplanets Anonymous (not verified) Tue, 12/08/2020 - 08:26 More News Jules Bernstein | UCR News December 08, 2020

UC Riverside is leading one of the NASA Astrobiology Program’s eight new research teams tackling questions about the evolution and origins of life on Earth and the possibility of life beyond our solar system.

The teams comprise the inaugural class of NASA’s Interdisciplinary Consortia for Astrobiology Research program. The UCR-led team is motivated by the fundamental question of how to detect planets that could host life and remain habitable despite tremendous change over time, which requires hunting for biological gases in the atmospheres of planets light years beyond our solar system.

This image shows an Earth-like "exomoon" orbiting a gas giant planet in a star's habitable zone. (NASA/JPL-Caltech)

“To achieve this goal, our research focuses on the many diverse chapters of Earth’s history — or alternative Earths — that span billions of years and offer critical templates for examining exoplanets far beyond our solar system,” said UCR biogeochemist Timothy Lyons, the project leader.

Because of their immense distance from us, humans will likely never visit those planets, at least not soon, Lyons said. However, in the near future, scientists will be able to analyze the compositions of these planets’ atmospheres, looking for gases like oxygen and methane that could come from life.

Earth has undergone dramatic changes over the last 4.5 billion years, with major transitions occurring in plate tectonics, climate, ocean chemistry, the structure of our ecosystems, and composition of our atmosphere.

“These changes represent an opportunity,” Lyons said. “The different periods of Earth’s evolutionary history provide glimpses of many, largely alien worlds, some of which may be analogs for habitable planetary states that are very different from conditions on modern Earth.”

Exciting new research frontiers for Lyons’ team include studies of Earth’s first 500 million years, as well as predictions about our planet and its life billions of years in the future.

Studying biosignature gases in Earth’s past will allow the team to design telescopes and refine interpretative models for potential traces of life in distant exoplanet atmospheres, noted Georgia Tech biogeochemist Christopher Reinhard.

Once the researchers understand how Earth and its star — the sun — changed together to maintain liquid oceans teeming with life over billions of years, the team can predict how other planetary systems might also have developed and maintained life and better understand how to search for it.

“Such a ‘mission to early Earth’ must include broad interdisciplinary within the team, impactful synergy within and across the Research Coordination Networks, or RCNs, of the NASA Astrobiology Program, and a commitment to deliverables that will help steer NASA science for decades to come,” said UCR astrobiologist Edward Schwieterman.

Success in this mission will require biological, chemical, geological, oceanographic, and astronomical expertise. Yale University biogeochemist Noah Planavsky said, “our team brings all that to the table.” Accordingly, the diverse expertise within the team includes astronomers, planetary scientists, geologists, geophysicists, oceanographers, biogeochemists, and geobiologists.

The team will collect ancient rock samples and modern sediments from around the world spanning billions of years and use the data they generate to drive wide-ranging computational models for Earth’s ancient and future oceans and atmospheres.

“The models will allow the team to evaluate whether different periods in Earth’s history were characterized by gases that would have been detectable from a distant vantage as products of life, much the way oxygen fingerprints life on our planet today,” said Purdue University Earth and exoplanetary scientist Stephanie Olson.

This work requires a multipronged view of the Earth as a complex system that has varied dramatically over time. Yet despite all the change, Earth has remained persistently habitable, with liquid water oceans teeming with life.

How Earth became and remained habitable and whether its life would have been detectable to a distant observer are the questions that will ultimately define and refine the search for life on exoplanets.

“In short,” said Lyons, “the exciting goal of our team is to provide a new and more holistic view of Earth’s evolutionary history in order to help guide NASA’s mission-specific search for life on distant worlds.”

The RCNs are the new face of astrobiology at NASA, following 20 years of exciting research under the umbrella of the NASA Astrobiology Institute, which supported the UCR-led team previously.

The $4.6 million new award from NASA will span five years and includes team members from Georgia Tech, Yale University, Purdue University, UCLA, NASA Ames Research Center and collaborators from around the world.

Tim Lyons and Edward Schwieterman contributed significantly to this story.

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Venus might be habitable today, if not for Jupiter

Anonymous — Fri, 09 Oct 2020 20:58:54 +0000

Venus might be habitable today, if not for Jupiter Anonymous (not verified) Fri, 10/09/2020 - 13:58 More News Jules Bernstein | UCR News September 30, 2020

Venus might not be a sweltering, waterless hellscape today if Jupiter hadn’t altered its orbit around the sun, according to new UC Riverside research.

Animation depicts eccentricities of the inner planet orbits, and illustrates how circular the orbit of Venus is. (ChongChong He)

Jupiter has a mass that is two-and-a-half times that of all other planets in our solar system — combined. Because it is comparatively gigantic, it has the ability to disturb other planets’ orbits.

Early in Jupiter’s formation as a planet, it moved closer to and then away from the sun due to interactions with the disc from which planets form as well as the other giant planets. This movement in turn affected Venus.

Observations of other planetary systems have shown that similar giant planet migrations soon after formation may be a relatively common occurrence. These are among the findings of a new study published in the Planetary Science Journal.

Scientists consider planets lacking liquid water to be incapable of hosting life as we know it. Though Venus may have lost some water early on for other reasons, and may have continued to do so anyway, UCR astrobiologist Stephen Kane said that Jupiter’s movement likely triggered Venus onto a path toward its current, inhospitable state.

“One of the interesting things about the Venus of today is that its orbit is almost perfectly circular,” said Kane, who led the study. “With this project, I wanted to explore whether the orbit has always been circular and if not, what are the implications of that?”

To answer these questions, Kane created a model that simulated the solar system, calculating the location of all the planets at any one time and how they pull one another in different directions.

Scientists measure how noncircular a planet’s orbit is between 0, which is completely circular, and 1, which is not circular at all. The number between 0 and 1 is called the eccentricity of the orbit. An orbit with an eccentricity of 1 would not even complete an orbit around a star; it would simply launch into space, Kane said.

Currently, the orbit of Venus is measured at 0.006, which is the most circular of any planet in our solar system. However, Kane’s model shows that when Jupiter was likely closer to the sun about a billion years ago, Venus likely had an eccentricity of 0.3, and there is a much higher probability that it was habitable then.

“As Jupiter migrated, Venus would have gone through dramatic changes in climate, heating up then cooling off and increasingly losing its water into the atmosphere,” Kane said.

Recently, scientists generated much excitement by discovering a gas in the clouds above Venus that may indicate the presence of life. The gas, phosphine, is typically produced by microbes, and Kane says it is possible that the gas represents “the last surviving species on a planet that went through a dramatic change in its environment.”

For that to be the case, however, Kane notes the microbes would have had to sustain their presence in the sulfuric acid clouds above Venus for roughly a billion years since Venus last had surface liquid water — a difficult to imagine though not impossible scenario.

“There are probably a lot of other processes that could produce the gas that haven’t yet been explored,” Kane said.

Ultimately, Kane says it is important to understand what happened to Venus, a planet that was once likely habitable and now has surface temperatures of up to 800 degrees Fahrenheit.

“I focus on the differences between Venus and Earth, and what went wrong for Venus, so we can gain insight into how the Earth is habitable, and what we can do to shepherd this planet as best we can,” Kane said.

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