” Were finding things on Mars that are tantalizingly interesting, but we would really require more evidence to state weve identified life,” stated Paul Mahaffy, who served as the primary investigator of the Sample Analysis at Mars (SAM) chemistry lab aboard Curiosity till retiring from NASAs Goddard Space Flight Center in Greenbelt, Maryland, in December 2021. “So were looking at what else could have triggered the carbon signature were seeing, if not life.”
In a report of their findings that was released in the Proceedings of the National Academy of Sciences journal on January 18, 2022, Curiosity scientists provide a number of explanations for the unusual carbon signals they identified. Their hypotheses are drawn partly from carbon signatures in the world, however scientists alert the 2 worlds are so different they cant make definitive conclusions based on Earth examples.
This image reveals the Highfield drill hole made by NASAs Mars Curiosity rover as it was collecting a sample on “Vera Rubin Ridge” in Gale Crater. Credit: NASA/Caltech-JPL/MSSS
” The hardest thing is releasing Earth and releasing that predisposition that we have and really trying to enter the basics of the chemistry, physics, and environmental processes on Mars,” said Goddard astrobiologist Jennifer L. Eigenbrode, who took part in the carbon study. Previously, Eigenbrode led a worldwide group of Curiosity researchers in the detection of myriad organic particles– ones which contain carbon– on the Martian surface area.
” We need to open our minds and believe outside the box,” Eigenbrode said, “and thats what this paper does.”
The biological explanation Curiosity researchers present in their paper is motivated by Earth life. It involves ancient germs in the surface that would have produced a distinct carbon signature as they released methane into the atmosphere where ultraviolet light would have transformed that gas into bigger, more intricate particles. These new particles would have rained down to the surface and now could be preserved with their distinct carbon signature in Martian rocks.
2 other hypotheses offer nonbiological descriptions. One suggests the carbon signature could have resulted from the interaction of ultraviolet light with co2 gas in the Martian environment, producing brand-new carbon-containing particles that would have settled to the surface area. And the other speculates that the carbon could have been left behind from an unusual event numerous countless years ago when the solar system travelled through a giant molecular cloud abundant in the type of carbon discovered.
Stitched together from 28 images, NASAs Curiosity Mars rover recorded this view from “Greenheugh Pediment” on April 9, 2020, the 2,729 th Martian day, or sol, of the mission. Credit: NASA/JPL-Caltech/MSSS
” All 3 descriptions fit the information,” said Christopher House, a Curiosity scientist based at Pennsylvania State University who led the carbon study. “We merely require more information to rule them in or out.”
The TLS determined the isotopes from some of the decreased carbon that was set totally free in the heating process. Isotopes are atoms of an element with various masses due to their distinct number of neutrons, and they are instrumental in understanding the chemical and biological advancement of worlds.
Carbon is particularly crucial given that this component is discovered in all life on Earth; it streams constantly through the air, water, and ground in a cycle thats well understood thanks to isotope measurements.
This low-angle self-portrait of NASAs Curiosity Mars rover reveals the car at the site from which it reached down to drill into a rock target called “Buckskin” on lower Mount Sharp. Credits: NASA/JPL-Caltech/MSSS
or instance, living animals in the world utilize the smaller sized, lighter carbon-12 atom to metabolize food or for photosynthesis versus the heavier carbon-13 atom. Hence, substantially more carbon-12 than carbon-13 in ancient rocks, in addition to other evidence, suggests to scientists theyre taking a look at signatures of life-related chemistry. Looking at the ratio of these two carbon isotopes assists Earth researchers tell what kind of life theyre looking at and the environment it lived in.
On Mars, Curiosity scientists discovered that nearly half of their samples had surprisingly big quantities of carbon-12 compared to what scientists have measured in the Martian environment and meteorites. These samples originated from five unique locations in Gale Crater, the researchers report, which may be related because all the places have unspoiled, ancient surface areas.
” On Earth, processes that would produce the carbon signal were finding on Mars are biological,” House said. “We have to understand whether the very same explanation works for Mars, or if there are other descriptions, because Mars is extremely various.”
Interests view from the top of the Greenheugh Pediment. Credit: NASA/JPL-Caltech/MSSS
Mars is unique since it may have begun with a different mix of carbon isotopes than Earth 4.5 billion years earlier. Mars is smaller, cooler, has weaker gravity, and various gases in its environment. In addition, the carbon on Mars could be cycling without any life involved.
” Theres a huge chunk of the carbon cycle in the world that involves life, and because of life, there is a portion of the carbon cycle in the world we cant comprehend, since everywhere we look there is life,” said Andrew Steele, a Curiosity researcher based at the Carnegie Institution for Science in Washington, D.C.
Steele noted that researchers are in the early phases of comprehending how carbon cycles on Mars and, therefore, how to analyze isotopic ratios and the nonbiological activities that might result in those ratios. Curiosity, which arrived on the Red Planet in 2012, is the very first rover with tools to study carbon isotopes in the surface area. Other missions have actually gathered information about isotopic signatures in the environment, and researchers have measured ratios of Martian meteorites that have actually been gathered in the world.
” Defining the carbon cycle on Mars is absolutely crucial to attempting to comprehend how life might fit into that cycle,” Steele stated. “We have actually done that actually effectively on Earth, however we are simply beginning to specify that cycle for Mars.”
Curiosity researchers will continue to measure carbon isotopes to see if they get a comparable signature when the rover visits other sites believed to have unspoiled ancient surfaces. To even more evaluate the biological hypothesis including methane-producing microorganisms, the Curiosity group would like to examine the carbon content of a methane plume released from the surface area.
Curiositys objective is led by NASAs Jet Propulsion Laboratory in Southern California; JPL is managed by Caltech.
For more on this research, see Newly Discovered Carbon on Mars: Origin May Be Biologically Produced Methane.
Recommendation: “Depleted carbon isotope structures observed at Gale crater, Mars” by Christopher H. House, Gregory M. Wong, Christopher R. Webster, Gregory J. Flesch, Heather B. Franz, Jennifer C. Stern, Alex Pavlov, Sushil K. Atreya, Jennifer L. Eigenbrode, Alexis Gilbert, Amy E. Hofmann, Maëva Millan, Andrew Steele, Daniel P. Glavin, Charles A. Malespin and Paul R. Mahaffy, 17 January 2022, Proceedings of the National Academy of Sciences.DOI: 10.1073/ pnas.2115651119.
One suggests the carbon signature could have resulted from the interaction of ultraviolet light with carbon dioxide gas in the Martian atmosphere, producing new carbon-containing particles that would have settled to the surface area. And the other speculates that the carbon might have been left behind from an unusual event hundreds of millions of years ago when the solar system passed through a huge molecular cloud abundant in the type of carbon spotted.
Mars is distinct since it may have begun off with a different mix of carbon isotopes than Earth 4.5 billion years earlier. Furthermore, the carbon on Mars could be cycling without any life involved.
” Theres a huge chunk of the carbon cycle on Earth that includes life, and because of life, there is a piece of the carbon cycle on Earth we cant comprehend, due to the fact that everywhere we look there is life,” said Andrew Steele, a Curiosity scientist based at the Carnegie Institution for Science in Washington, D.C.
Steele noted that scientists researchers in the early stages phases understanding comprehending carbon cycles on Mars and, thusTherefore how to interpret translate ratios and the nonbiological activities that could might to those ratios.
NASAs Curiosity Mars rover caught these clouds simply after sundown on March 19, 2021, the 3,063 rd Martian day, or sol, of the rovers objective. The image is made up of 21 private images sewn together and color-corrected so that the scene looks like it would to the human eye. Credit: NASA/JPL-Caltech/MSSS
The kind of carbon is related to biological procedures on Earth. Curiosity scientists offer numerous descriptions for the uncommon carbon signals.
After examining powdered rock samples collected from the surface area of Mars by NASAs Curiosity rover, scientists have actually announced that numerous of the samples are abundant in a kind of carbon that on Earth is related to biological procedures.
While the finding is intriguing, it doesnt always point to ancient life on Mars, as scientists have not yet found conclusive supporting evidence of existing or ancient biology there, such as sedimentary rock formations produced by ancient germs, or a variety of complex natural molecules formed by life.
