Life in our backyard?

Last week NASA made an announcement about possible life-supporting conditions on two solar system moons, Enceladus (One of Saturn’s moons) and Europa (One of Jupiter’s moons). While the two gas giants in our solar system are likely not capable of hosting life as we know it, some of their moons make good candidates. Life needs the right chemistry to start and be sustained. The common requirement of all life on earth is liquid water, energy, and a cocktail of ingredients including carbon, oxygen, nitrogen, hydrogen, and other elements. The energy can come from anywhere — up at the surface from the sun, or from hydrothermal vents deep in the ocean, for example. On moons of giant planets, energy can even come from the push and pull  from the parent planet as it orbits. Habitability is definitely not limited to planets!

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Hydrothermal vents on Earth’s ocean floor provide a food source for deep sea microbes and support an sun-less ecosystem. Credit: Wikipedia/NOAA

The Cassini mission, famous for many gorgeous views of saturn and its rings, was able to fly nearby Saturn’s moon Enceladus, to try to catch a whiff of what might be coming off the moon using its Ion and Neutral Mass Spectrometer (INMS). To scientists’ delight, they discovered hydrogen gas coming off the surface of Enceladus, indicating hydrothermal vents injecting hydrogen into the subsurface ocean. The findings suggest an environment not unlike the deep sea vents supporting parts of Earth’s ocean ecosystem.

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An illustration of the Cassini flyby of Enceladus detecting plumes of hydrogen gas. Credit: NASA/JPL-Caltech

Meanwhile, using our old pal Hubble, a team of astronomers found evidence for water plumes on Europa. An earlier study discovered Europa’s saline liquid water ocean by measuring the magnetic field changes with the Galileo spacecraft as it flew by in 2000. The latest study describes ultraviolet observation’s with HST/STIS that show absorption at a location consistent between two observations on Europa. The possible plumes lie right on top of a hot spot previously discovered on the surface. The plumes could be the result of an eruptive disruption to the surrounding ice shell. How the ice shell gets disrupted is still unknown but has implications on either its thickness or other physical processes on Europa.

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Evidence of plumes coming off the surface of Europa in two different observations. High resolution images of Europa are overlaid on top of the Hubble data to more clearly show the location of the plumes. Credit: NASA/ESA/STScI/USGS

Both these latest finds come on top of many previous missions and observations studying these solar system bodies. Learning about the compositions and structures of solar system moons allows scientists to interpret new exciting discoveries like these, and importantly, know what to look for when designing new missions and pointing our favorite telescopes.

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