by Does life exist in other parts of the world? If so, how do scientists search for and identify it? Finding life beyond Earth is extremely difficult, partly because other planets are so far away and partly because we’re not sure what to look for.
However, astrobiologists have learned a lot about how to find life in extraterrestrial environments, mainly by studying how and when Earth became livable.
While NASA research teams are directly combing the surface of Mars for signs of life, our interdisciplinary research group is using a site here on Earth to approximate the ancient environmental conditions on Mars.
The Middle Miocene Clarkia Fossil Site of northern Idaho contains sediments that preserve some of the most diverse biological marker molecules, or biomarkers, in the world. These are remnants of the past that provide insight into Earth’s history.
An ancient lake
About 16 million years ago, a lava flow from Clarkia, Idaho, damaged a local drainage system and created a deep lake in a narrow, steep valley. Although the lake has since dried up, weathering, erosion and human activity have exposed sediments from the former lake bed.
For nearly five decades, research teams like ours – led by Dr. Hong Yang and Dr. Qin Leng – using fossil remains and biogeochemistry to reconstruct past environments of the Miocene Clarkia Lake region.
The depth of the lake created the perfect conditions to protect the microbial, plant and animal remains that fell to the bottom of the lake. In fact, the sediments are so well preserved that some of the fossilized leaves still show their autumn colors from when they went into the water millions of years ago.
Today, ancient lake beds on Earth are becoming important sites for learning about habitable environments on other planets.
Biological marker molecules
Clarkia lake sediments contain a series of ancient biomarkers. These compounds, or classes of compounds, can reveal how organisms and their environments functioned in the past.
Since the discovery of the Clarkia fossil site in 1972, numerous research teams have used a variety of cutting-edge technologies to analyze various biomarkers.
Some of those found in Clarkia include lignin, which is the structural support tissue of plants, lipids such as fats and waxes, and possibly DNA and amino acids.
Understanding the origin, history and environmental factors that have allowed these biomarkers to remain so well at Clarkia may enable our team to explore the potential of material conservation. predicting organisms in ancient lake deposits on Mars.
Studying the signatures of life on Mars
In 2021, the Mars Perseverance Rover landed on top of the lake deposits in Mars’ Jezero Crater. Jezero is a meteorite impact crater believed to have once been flooded with water and home to an ancient river delta. Microbial life may have lived in the Jezero crater lake, and their biomarkers may be found in lake bed sediments today. Persistence is drilling into the surface of the crater to collect samples that may contain ancient signs of life, with the intention of returning the samples to Earth in 2033.
Clarkia has many similarities with the Jezero Crater. Both Clarkia and Jezero Crater contain ancient lake deposits derived from siliceous basaltic rock that formed under a climate of higher temperatures, high humidity and a carbon dioxide rich atmosphere.
At Clarkia, these conditions preserved microbial biomarkers in the ancient lake. Lakes may have formed at similar sites on the surface of Mars.
The samples being collected by Persistence contain the geological and climatic history of the Jezero Crater landing site and may even contain preserved biomarkers of ancient life.
While Persistence continues its mission, our group is establishing criteria for biomolecular authentication. That means we’re developing ways to determine whether ancient biomarkers from Earth, and hopefully Mars, are true echoes of life—rather than recent contamination or molecules from nonliving sources.
To do so, we are studying biomarkers from Clarkia fossil leaves and sediments and developing laboratory experiments using Martian simulations. This material simulates the chemical and physical properties of Jezero Crater lake sediments.
By unraveling the sources, history and preservation of the biomarkers associated with the ancient Clarkia lake deposits, we hope to develop new strategies for studying the Perseverance Rover samples once they are back on Earth.
This article is republished from The Conversation, a non-profit, independent news organization that brings you reliable facts and analysis to help you make sense of our complex world. It was written by: Robert Patalano, Bryant University
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Robert Patalano receives funding from NASA’s Rhode Island Space Grant Program.
