Joint UTSA-SwRI study shows how radioactive decay could support extraterrestrial life
(May 22, 2017) -- In the icy bodies around our solar system, radiation emitted from rocky cores could break up water molecules and support hydrogen-eating microbes. To address this cosmic possibility, a University of Texas at San Antonio (UTSA) and Southwest Research Institute (SwRI) team modeled a natural water-cracking process called radiolysis. They then applied the model to several worlds with known or suspected interior oceans, including Saturn's moon Enceladus, Jupiter's moon Europa, Pluto and its moon Charon, as well as the dwarf planet Ceres.
"The physical and chemical processes that follow radiolysis release molecular hydrogen (H2), which is a molecule of astrobiological interest," said Alexis Bouquet, lead author of the study published in the May edition of Astrophysical Journal Letters.
Radioactive isotopes of elements such as uranium, potassium, and thorium are found in a class of rocky meteorites known as chondrites. The cores of the worlds studied by Bouquet and his co-authors are thought to have chondrite-like compositions. Ocean water permeating the porous rock of the core could be exposed to ionizing radiation and undergo radiolysis, producing molecular hydrogen and reactive oxygen compounds.
Bouquet, a student in the joint doctoral program between UTSA's Department of Physics and Astronomy and SwRI's Space Science and Engineering Division, explained that microbial communities sustained by H2 have been found in extreme environments on Earth, including a groundwater sample found nearly 2 miles deep in a South African gold mine and at hydrothermal vents on the ocean floor. That raises interesting possibilities for the potential existence of analogous microbes at the water-rock interfaces of ocean worlds such as Enceladus or Europa.
"We know that these radioactive elements exist within icy bodies, but this is the first systematic look across the solar system to estimate radiolysis. The results suggest that there are many potential targets for exploration out there, and that's exciting," says co-author Danielle Wyrick, a principal scientist in SwRI's Space Science and Engineering Division.
The most frequently considered source of molecular hydrogen on ocean worlds is serpentinization, a chemical reaction between rock and water that occurs around hydrothermal vents on Earth's ocean floor. Through this process, volcanic activity emits hot, mineral-laden fluids, allowing unique microbial ecosystems to thrive in otherwise cold, dark regions.
The key finding of the study is that radiolysis represents a potentially important additional source of molecular hydrogen. While hydrothermal activity can produce considerable quantities of hydrogen, in porous rocks often found under seafloors, radiolysis could produce copious amounts as well.
Radiolysis may also contribute to the potential habitability of ocean worlds in another way. In addition to molecular hydrogen, it produces oxygen compounds that can react with certain minerals in the core to create sulfates, a food source for some kinds of microorganisms.
"Radiolysis in an ocean world's outer core could be fundamental in supporting life. Because mixtures of water and rock are everywhere in the outer solar system, this insight increases the odds of abundant habitable real estate out there," Bouquet said.
Co-authors of the article, "Alternative Energy: Production of H2 by Radiolysis of Water in the Rocky Cores of Icy Bodies," are SwRI's Christopher R. Glein, Wyrick, and J. Hunter Waite, who also serves as a UTSA adjoint professor.
UTSA is ranked among the top 400 universities in the world and among the top 100 in the nation, according to Times Higher Education.
- Deb Schmid
Learn more about the UTSA Department of Physics and Astronomy.
Learn more about the SwRI Space Science and Engineering Division.
The UTSA SBDC Technology Commercialization Center is hosting this 3-day event featuring SBIR/STTR proposal workshops, business model development sessions and the DoD Navy Innovation Summit. Hear from industry experts, entrepreneurs and more.Durango Building, El Mercado Room (DB 1.204C), Downtown Campus
Part of "Brewing Up Texas" exhibit programs, this event focuses on seasonal beers and why certain beers are brewed and served in winter months.Institute of Texan Cultures, Hemisfair Campus
This high school student exhibit features images, videos, interviews and writings that the students learned about while participating in "The Will to Adorn: African American Dress and the Aesthetics of Identity."Institute of Texan Cultures, Hemisfair Campus
This ceremony honors graduates from the College of Business, College of Engineering, the College of Public Policy and College of Sciences. U.S. Representative Joaquin Castro will deliver the keynote address.Alamodome. 100 Montana St., Downtown San Antonio
Graduates from the College of Architecture, Construction and Planning, College of Education and Human Development, College of Liberal and Fine Arts, and University College will hear from Mayor Ron Nirenberg.Alamodome. 100 Montana St., Downtown San Antonio
President Taylor Eighmy invites UTSA faculty and staff to Tacos With Taylor. Take this opportunity to introduce yourself to Dr. Eighmy at any one of these casual meet and greets. Breakfast tacos will be served while supplies last.Institute of Texan Cultures, Hemisfair Campus
Join the UTSA Small Business Development Center for a day of learning, skill-building, and professional development that will kick-start your small business ambitions in 2018.Institute of Texan Cultures, Hemisfair Campus
Join the UTSA contingent for the city-wide march to honor Dr. Martin Luther King, Junior. This event is open to all UTSA students, faculty, staff, alumni, and their families.Downtown San Antonio