The day when human beings finally set foot on Mars is rapidly approaching. Right now, NASA, the China National Space Agency (CNSA), and SpaceX have all announced plans to send astronauts to the Red Planet “by 2040”, “in 2033”, and “before 2030”, respectively. These missions will lead to the creation of long-term habitats that will enable return missions and scientific research that will investigate everything from the geological evolution of Mars to the possible existence of past (or even present) life. The opportunities this will create are mirrored only by the challenges they will entail.
One of the greatest challenges is ensuring that crews have access to water, which means that any habitats must be established near an underground source. Similarly, scientists anticipate that if there is still life on Mars today, it will likely exist in “briny patches” beneath the surface. A possible solution is to incorporate a system for large-scale water mining operations on Mars that could screen for lifeforms. The proposal, known as an Agnostic Life Finding (ALF) system, was one of thirteen concepts selected by NASA’s Innovative Advanced Concept (NIAC) program this year for Phase I development.
The concept was proposed by Steven Benner and a team from the Foundation for Applied Molecular Evolution (FfAME) in Alachua, Florida. Benner is a former professor of chemistry at Harvard University, ETH Zurich, and the University of Florida, where he was the V.T. & Louise Jackson Distinguished Professor of Chemistry. In 2005, he founded the Foundation For Applied Molecular Evolution, where he and his colleagues became the first scientists to synthesize a gene, thus giving birth to the field of synthetic biology.
As Benner and his team explained in their proposal, the ALF system is designed to simplify astrobiological studies on Mars before any crewed missions arrive. Its purpose is also to address several foregone conclusions raised at NASA’s 2019 Conference (Extant Life on Mars: What’s Next?) held in Carlsbad, New Mexico. During this conference, it was generally agreed that scientists have good reason to suspect the following about life on Mars:
Life started on Mars using the same geo-organic chemistry that started life on Earth. Martian life persists today on Mars, in near-surface ice, low elevations, and caves, all with transient liquid brines, environments that today on Earth host microbial life. Martian life must use informational polymers (like DNA); Darwinian evolution requires these, and Darwinian evolution is the only way matter can organize to give life. While Martian “DNA” may differ (possibly radically) in its chemistry from Terran DNA, the “Polyelectrolyte Theory of the Gene” limits the universe of possible alien DNA structures. Those structures ensure that Martian DNA can be concentrated from Martian water, even if very highly diluted, and even if Martian “DNA” differs from Earth DNA. On Mars, as it exists today, information polymers cannot be generated without life (unlike other less reliable biosignatures such as methane), ensuring that life will not be “detected” if it is not present (the “false positive problem”).Citing a previous study by SETI Institute senior scientist John D. Rummel and NASA Planetary Protection Officer (PPO) Catherine A. Conley, Benner and his team note that there are several fallacies when it comes to proposed efforts to search for extant evidence of Martian life. Addressing the planetary protection policy of the Committee on Space Research (COSPAR), Rummel and Conley concluded that there are four significant “shortcomings in their plans to look for evidence of life on Mars.” First, they addressed the contention that appropriate levels of spacecraft cleanliness are unaffordable.
Second, they challenged claims that there are major risks in assuming life could be identified through nucleic acid sequence comparison, especially if those sequences are obtained from a “Special Region” contaminated with Earth life. They also challenge the contention that present-day exploration by “dirty robots” is preferable to the possibility of contamination spread by future human exploration and that the potential effects of contaminating resources and environments essential to future human missions to Mars were not being addressed. Based on these considerations, Rummel and Conley concluded that scientists did not consider the detection of extant life on Mars “a high priority.”
Graphic depiction of the Agnostic Life System (ALF) to screen for introduced and alien life. Credit: Steven Benner
According to Benner and his colleagues, the purpose of this NIAC project is to change this view before the arrival of crewed missions, which will undoubtedly complicate the search for indigenous Martian life. Therefore, the plans for crewed missions in the coming decades place a very strict deadline on the search or life on Mars, but also offer an opportunity that can be exploited. In particular, Benner and his team indicate how mission proposals emphasize the need for in-situ resource utilization (ISRU), especially where near-surface water ice is concerned. As they wrote:
“Propellant (methane and oxygen) will be generated from that water and atmospheric carbon dioxide for the return trip back to Earth. That water ice will be mined on the scale of tens to hundreds of tons. Further, to maximize the likelihood of safe return of the crew to Earth, robotic operations that mine tons of near-surface water ice will be in place before the first human astronauts arrive. Thus, water mined in preparation for human arrival is correctly seen as an extremely large-scale astrobiological sample, far larger than dry cached rocks.”
The mined water ice, they claim, will contain dust deposited over time by Martian dust storms, allowing scientists to obtain information about the accessible surface of Mars. Therefore, the massive sample of water ice will enable a highly sensitive survey of the Martian surface for potential signs of life. The ALF system will allow for the extraction of genetic polymers – be they alien or the result of contamination from robotic missions. The ALF system also offers tools to conduct partial in-situ analysis of any polymers that dissociate in water (polyelectrolytes).
According to Benner, the system is called “agnostic” because of how it “exploits what synthetic biology taught us about the limited kinds of Darwinian genetic molecules.” Since it is an add-on system, including an ALF system represents a negligible burden in terms of mass and energy to any existing mining operation. Despite that, it will allow for science operations that will establish a strict lower limit on the amount of biomaterial that is accessible on the Martian surface and will do so before a human presence is established on Mars.
As Benner and his team summarized, the system will also be useful on other bodies humanity hopes to explore for signs of life (and possibly settle) someday. “[I]t will do so before Homo sapiens becomes a multiplanetary species. And “multiplanetary” is the correct term,” they wrote. “This add-on ALF system can be used on all celestial bodies where water will be mined to search for and analyze life, indigenous or introduced, Earth-like or alien. This includes Europa, Enceladus, the Moon, and exotic locales on Earth.”
Further Reading: NASA
