A chemical analysis of a vast ocean on the moon shows life most likely doesn’t exist, says a report co-authored by a USF astrobiologist.
Although the phase of this moon might appear familiar, the moon itself might not. In fact, this gibbous phase shows part of Jupiter's moon Europa. The robot spacecraft Galileo captured this image mosaic during its mission orbiting Jupiter from 1995 - 2003. Visible are plains of bright ice, cracks that run to the horizon, and dark patches that likely contain both ice and dirt. Raised terrain is particularly apparent near the terminator, where it casts shadows. Europa is nearly the same size as Earth's Moon, but much smoother, showing few highlands or large impact craters. Evidence and images from the Galileo spacecraft, indicated that liquid oceans might exist below the icy surface. Photo courtesy of NASA.
By Vickie Chachere
TAMPA, Fla. (March 6, 2012) – Those speculating on whether Jupiter’s moon, Europa, might be harboring life in a vast ocean underneath a thick layer of ice might now have the answer: probably not, says a new study co-authored by a USF astrobiologist.
USF Assistant Professor of Geology Matthew Pasek
The ocean underneath the ice layer of Europa is likely too acidic to support larger life forms, dousing hopes by those who thought the indication of water on the Jupiter moon might be a place where extraterrestrial life could be found. The new chemical analysis by Assistant Professor of Geology Matthew Pasek and Richard Greenberg of the University of Arizona’s Department of Planetary Science, says the Europan sea environment is probably not friendly to marine life as we know it.
Space scientists have focused on Jupiter and Europa since the Galileo spacecraft, launched by the space shuttle Atlantis in 1989, provided scientists with decades of data to analyze. One of its most significant discoveries was the inference of a global salt water ocean some 100-miles deep on Europa. The ocean is estimated to be deep enough to cover the whole surface of Europa and contains more than three times the water of all of Earth's oceans combined.
On Earth, water generally means life – but that’s not likely so on Europa, Pasek and Greenberg report in the journal Astrobiology after analyzing computer models of Europa’s ocean.
Oxygen is a major component of Europa’s crust. But unlike Earth with its photosynthetically-derived oxygen, the oxygen on Europa is formed by the high-energy bombardment of Europa’s surface by radiation, Pasek explains.
The scientists used computer models to calculate the predicted chemistry of Europa – the same technology that’s designed to predict Earth’s groundwater chemistry or water chemistry at phosphate mines. After generating data on the inputs of oxygen descending into the crust, the scientists estimated the amount of material coming out of the rocks beneath the ocean.
This global view of Europa shows the location of a four-frame mosaic of images taken by NASA's Galileo spacecraft, set into low-resolution data obtained by the Voyager spacecraft in 1979. Putting new data into its surrounding context is a technique that allows scientists to better understand features observed on planetary surfaces. The Galileo spacecraft obtained these images during its first orbit of Jupiter at a distance of 156,000 km (96,300 miles) on June 27, 1996. The finest details that can discerned in this picture are about 1.6 kilometers (1 mile) across. North is to the top. For details on the Galileo images in this release, click here. Photo courtesy of NASA.
The oxygen reacts with sulfur and other materials emanating from rocks at the bottom of the ocean. “When the two meet, they generate acid - sulfuric acid in this case,” Pasek said. That would produce water with a pH of about 2.6, "about the same as your average soft drink," Pasek said. “Just as soft drinks are bad for your teeth as they are quite acidic, fish, corals, whales, or other large animals would find it difficult to live within the ocean of Europa.”
Those acidic levels would make it impossible for marine organisms like the ones found on Earth to grow shells or develop the way early marine organisms have here.
That said, if there is life on Europa it might look more like the microbes found near acid mines in Spain who thrive in the Rio Tinto. Those organisms have evolved to oxidize iron and sulfide as energy sources, and tolerate environments even more acidic than those predicted for Europa.
"The microbes there have figured out ways of fighting their acidic environment," Pasek said. "If life did that on Europa, [Jupiter's moon] Ganymede, and maybe even Mars, that might have been quite advantageous."
The full paper can be read here.
Vickie Chachere can be reached at 813-974-6251.