ScienceCasts: Ocean Worlds
We once thought oceans made our planet unique, but we’re now coming to realize that ‘ocean worlds’ are all around us. Earth. A world dominated by water. Trillions of gallons flow freely across the surface of our blue-green planet. While we once thought oceans made our planet unique, we’re now coming to realize that ‘ocean worlds’ are all around us.
Our planet retains its atmosphere and in turn its abundance of liquid water thanks, in part, to a very strong magnetic field, which provides protection from the solar wind. Without this magnetic field our atmosphere would be stripped away leaving the pale blue dot looking more like… one of our neighbors? Scientists believe Venus’ early oceans evaporated. With no water left on the surface, carbon dioxide built up in the atmosphere, leading to a runaway greenhouse effect that created present conditions. Likewise, Mars appears to have had oceans long ago. But the Red Planet’s global magnetic field decayed, leaving it vulnerable to atmospheric erosion by the solar wind.
Farther from the sun in the sub-freezing temperatures of the outer solar system, it may seem impossible for liquid water to exist. However, not only does it exist, but it some places it may be more abundant than on Earth! Jupiter is orbited by at least three moons that contain oceans; Europa, Ganymede, and Callisto.
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Thursday at 2 pm Eastern, NASA announced some exciting new findings about “oceans beyond Earth.” The announcement streamed live on NASA TV at 2 pm, but you can watch the replay right here.
The gist of the announcement: NASA has found the most compelling evidence yet that the ocean underneath the icy crust of Enceladus, Saturn’s sixth-largest moon, could contain life. In the past, the Cassini spacecraft has observed jets of water containing organic chemicals streaming from Enceladus. This latest finding adds a key ingredient for life to the mix: hydrogen. The presence of hydrogen in the jets makes NASA scientists suspect there are geothermal geysers on Enceladus’s ocean floor. Like the geothermal vents deep within Earth’s oceans, these could be home to microbes that use the chemical energy of hydrogen and carbon dioxide to produce methane and energy for life.
Also today, NASA announced it has collected more (not-yet-conclusive) evidence that there are also water vapor plumes emanating from Europa, Jupiter’s icy moon.
In the last leg of its life, Cassini keeps generating fascinating insights
The Cassini mission is at the end of an impressive 20-year run. In its final days, the spacecraft has been churning out intriguing discoveries. Today’s announcement adds one more to the list.
In 2004, Cassini became the first spacecraft to orbit Saturn. In its explorations of the planet’s magnetosphere and various moons, it has found evidence of an underground ocean on Enceladus. On the moon Titan, it revealed surprisingly Earthlike geographic features and great lakes of liquid natural gas on its surface that outweigh all the oil and gas reserves on Earth. It learned how new moons could form out of Saturn’s rings. And it has taken detailed, beautiful photographic surveys of the planet’s rings and surface features.
Now it’s beginning a series of harrowing orbits that bring it into the space between the planet and its rings — a region no spacecraft has been before. When Cassini is in the inner rings, it will finally be able to take the measurements that will aid in calculations to determine the mass of the rings.
Come September, the 20-year-old spacecraft will crash into Saturn, having spent all of its fuel. But the death dive isn’t just for fireworks. If Cassini doesn’t plunge into Saturn’s atmosphere, it runs the risk of potentially contaminating one of the planet’s moons with debris and microbes from Earth.
Cassini’s dramatic finale is also a last chance to squeeze some more insights out of the 20-year-old spacecraft. As the craft descends into Saturn’s atmosphere, “several of the instruments will be on,” including the mass spectrometer, Preston Dyches, a NASA spokesperson says. This instrument essentially can “sniff” the atmosphere and determine the chemical compounds it’s composed of.
When Cassini finally goes offline in September, it will die doing what it’s been doing all along: exploring.