Cassini tastes alien ocean on deep dive through icy plumes
Wednesday, October 28, 2015, 10:49 PM - Stay tuned for some potentially amazing science from the outer solar system. On Wednesday, NASA's Cassini spacecraft flew through plumes of water vapour streaming away from the surface of Saturn's icy moon, Enceladus.
Nearly two weeks ago, NASA's Cassini spacecraft made the first of three close flybys past the moon of Enceladus, passing over its north pole at a distance of about 1,800 kilometres.
Today, Wednesday, October 28, the second flyby took place, with the spacecraft flying over the moon's south pole, not simply for a matter of comparison, but also to perform a feat of orbital derring-do in the name of science!
According to NASA:
NASA's Cassini spacecraft successfully completed its close flyby of Saturn's moon Enceladus today, passing 30 miles (49 kilometers) above the moon's south polar region at approximately 8:22 a.m. PDT (11:22 a.m. EDT). Mission controllers established two-way communication with the spacecraft this afternoon and expect it to begin transmitting data from the encounter this evening. Images are anticipated in the next 24 to 48 hours.
Buzzing over Enceladus' surface at a height of just 49 kilometres, Cassini flew through plumes of water vapour that stream from long fissures in the southern hemisphere. Opening up its sensors to these plumes and snapping a multitude of images during this maneuver, the science team collected data that they hope will give them new insight into the source of the plumes - Enceladus' deep, global subsurface ocean.
While the mission isn't equipped to specifically search for signs of life in the plumes, the presence of a warm, salty liquid water ocean under Enceladus' crust does bring the possibility of life existing there, and Cassini can at least give a better understanding of how "friendly" this icy moon actually is to life as we know it.
According to NASA's pre-flythrough update:
Cassini scientists are hopeful the flyby will provide insights about how much hydrothermal activity -- that is, chemistry involving rock and hot water -- is occurring within Enceladus. This activity could have important implications for the potential habitability of the ocean for simple forms of life. The critical measurement for these questions is the detection of molecular hydrogen by the spacecraft.
Scientists also expect to better understand the chemistry of the plume as a result of the flyby. The low altitude of the encounter is, in part, intended to afford Cassini greater sensitivity to heavier, more massive molecules, including organics, than the spacecraft has observed during previous, higher-altitude passes through the plume.
The flyby will also hopefully reveal exactly how much material is being spewed out into space along these fissures, which will give some indication of how long the plumes have been active, and thus how long Enceladus has been active below its surface.
Although Cassini has made several passes through Enceladus' plumes by now, this will be the closest fly through ever. The first such pass took place in March 2008, flying through the plume at a distance of around 200 kilometres. In the years after, repeated flybys got closer, passing through different "layers" of the plume, and at distances as close as around 75 km. This 49 km pass promises some of the best results yet.