An ocean covers Saturn’s moon Enceladus. It’s covered by a frozen shell, but where this shell is cracked, liquid shoots high into space.
On Oct. 28, the spacecraft Cassini will sweep through this liquid and analyze its cocktail of chemicals to give scientists an understanding of the moon’s alien ocean.
Scientists are particularly interested in finding out whether the spouts come from hydrothermal vents on the seafloor. On Earth, active hydrothermal vents teem with life, and scientists even suspect that it is here that life first evolved on our planet. If Saturn’s moon Enceladus also had active hydrothermal vents it would indicate that the icy moon could support life.
ResearchGate spoke with Dr. Hunter Waite, team leader for Cassini’s neutral mass spectrometer instrument (INMS) at the Southwest Research Institute in San Antonio, Texas. He tells us about the mission and what he hopes to discover.
ResearchGate: Can you explain what it will be like for Cassini to fly through Enceladus’ cosmic shower?
Hunter Waite: Cassini will fly through a shower of very fine sleet (ice grains smaller than a micrometer in radius) at a speed of more than seven kilometers per second. The gas that is mixed in with the sleet is so thin that it will have almost no effect on the spacecraft. As Cassini sweeps through the mixture, the sensitive instrumentation on board will be able to detect what the ice and gas are made of in the hopes of revealing new information about the processes occurring in the internal ocean.
RG: What causes these amazing plumes to be shot up from Enceladus? How were they discovered?
Waite: The ocean is vented by small cracks in the ice to the vacuum of space, which draws out the material due to the pressure gradient. The plumes were first discovered because of the way in which the ice and gas effect the local plasma environment of Saturn’s magnetosphere. The changes in the magnetic field brought about by this process were first measured by the sensitive magnetometer onboard the spacecraft when it was in the vicinity of Enceladus.
RG: Cassini is only flying 30 miles above the surface of the moon. Are there any special challenges or dangers in getting this close?
Waite: There are always some dangers in a new environment, but the many measurements that have been made on previous flybys give us confidence that Cassini will be OK.
RG: How will Cassini sample and analyze the water as it sweeps through it?
Waite: Cassini will sample the water, ice and trace materials embedded in the gas and ice using both gas and ice mass spectrometers.
RG: What do you hope to find by flying through the plume?
Waite: We are looking for new information about the hydrothermal processes in the internal ocean. Measuring molecular hydrogen will almost assure us that the oceans have active hydrothermal vents, like in the Earth’s oceans (e.g. Lost City in the Atlantic).
RG: What discovery would provide the most convincing case for life?
Waite: Hydrothermal activity will suggest similar conditions to those that lead to life in Earth’s oceans and perhaps the same will be true at Enceladus. However, we will need future missions with similar but more capable instrumentation to verify this.