By Matt A. Barr
The prospect of life existing on other worlds has manifested itself in human culture for millennia. In a way, aliens have been visiting us ever since we could communicate. They’ve been the subject of our stories, our works of art, and even our religions, conjuring vivid worlds and exotic forms limited only by the imaginations of those who entertain them. Science fiction is often the realm of the alien, but very much embedded in fact is the potential to find alien life right here in our own solar system.
As discussed in previous posts, the conditions under which life as we know it may exist must include the presence of liquid water. Microbial life stretches our definitions of those conditions, and microbes are what we’re likely to find if we do discover alien life. With the recent discovery of flowing water on Mars, as well as our increasing understanding of microbiology, finding life on other worlds seems to be simply a matter of time. Luckily, we know what microbial life looks like here on Earth, and we know what conditions it can thrive in, meaning we can minimize that time by pointing our sights toward the stars to find where else those conditions might exist.
It turns out, they exist on Europa.
If there’s life anywhere else in our solar system, it’s probably on Europa. Europa is a mysterious icy moon orbiting Jupiter that has gripped the curiosity of planetary scientists for several decades. First discovered by Galileo in 1610, it would be more than four centuries before anyone turned their attention to the secrets it may hold.
While telescopes have been trained on Europa for some time, NASA’s Galileo mission in the late 1990’s produced some tantalizing data about the moon. Europa appears to be the most active planetary body in our solar system besides Earth. It’s estimated that roughly 100-150 km of an outer shell consisting of ice and a subsurface ocean completely encircle Europa’s silicate crust, and the interaction between these three features on Europa is of great interest to the scientific community.
Dr. Britney Schmidt, a planetary scientist at the Georgia Tech School of Earth and Atmospheric Sciences, and her research team, consisting of graduates Heather Chilton and Jacob Buffo, and undergraduate Josh Hedgepeth, are fascinated by the potential to harbor life that Europa holds. Understanding Europa’s planetary processes is critical to answering its habitability questions though. By conducting important research at ice shelves in Antarctica, specifically at the areas where ocean and ice directly interact with one another, Dr. Schmidt and her team hope to develop a working analog to what’s happening at the same types of physical boundaries on Europa. Doing so would go a long way towards answering some of those questions.
At Antarctica’s McMurdo Ice Shelf, Dr. Schmidt and scientists from several other universities collaborate to gather data about the ice by sending robotic probes into the water below. As part of a project known as SIMPLE (Sub-Ice Marine and PLanetary-analog Ecosytems), funded by NASA’s Astrobiology Science and Technology for Exploring Planets program, multiple expeditions scheduled over several “seasons” offer extraordinary opportunities to deploy up to five different submersibles into these frigid, unexplored waters. These submersibles are used to collect samples, make observations about the water column, and seek to determine what processes govern the highly dynamic relationship between the surface of the ocean and the bottom layer of the ice shelf. One of these submersibles, the Icefin, was designed and built by Dr. Schmidt’s startup here at Georgia Tech, and is slated for new upgrades between now and the upcoming Antarctic field expeditions. These upgrades will allow the Icefin to operate in much wider areas than are currently possible to explore.
We know that the Antarctic ice shelves can serve as analogs for Europa’s ice shell, but is there anything about Europa besides its liquid water that indicates the possible presence of life? It’s not so much that liquid water exists on Europa as it is the reasons why the water is there in the first place. Scarred with massive crevasses and chasms, Europa’s icy surface tells the story of significant geologic activity below. One hypothesis for the source of this geologic activity is that Jupiter’s gravity is pushing and pulling on Europa, depending on the relative position of one to the other. This is similar to the Earth-moon gravitational relationship we experience here, except that rather than merely changing the tides, Jupiter causes Europa’s interior to flex such that the resulting friction is likely causing Europa to heat up. This thermal energy is robust enough to maintain liquid water above Europa’s crust. Being outside of the habitable zone, however, Europa’s liquid water freezes over at a specific, as yet unknown depth to form the ice shell we observe.
This heating of Europa’s interior seems to result in the geologic activity that transports non-ice material from Europa’s crust toward its surface. This material is visible to us in the form of dark reddish-brown areas scattered all across Europa’s surface, and it’s these areas that are the most likely candidates for hosting the first alien life we could encounter, to say nothing of what might exist in the ocean itself. Similar non-ice material – material that happens to support life – is consistently observed in ice shelves on our planet. The ocean-ice-continent interaction occurring beneath these ice shelves, powered by the earth’s geologic activity, deposits this material into the ice via convection processes. The thinking goes that if we can understand how that’s happening on Earth, we will understand how it might be happening on Europa also.
As it happens, habitability questions are also climate science questions. Dr. Schmidt’s research ends up serving another purpose aside from understanding how alien life might develop on ice moons. Her team’s submersibles are looking at how the oceans change the ice shelves and vice-versa, which addresses some particularly crucial gaps in our knowledge of the mechanics governing how climate change affects our Polar Regions. Killing two birds with one stone is something we like to do here at Georgia Tech.
A final note of congratulations is in order. Dr. Schmidt has recently been appointed to the science definition team for NASA’s Large UV/Optical/Near-Infrared (LUVOIR) telescope project. She also has a few other exciting announcements whose releases we don’t wish to precede here, but she’s representing Georgia Tech and EAS in some pretty great ways. Check out EAS in the coming days and weeks for the details.
Update: We’re proud to announce that Dr. Britney Schmidt has been selected to join the board of directors for The Planetary Society. For more info about this appointment, see the Georgia Tech College of Sciences story.