The agency has selected nine science instruments for the trip, which is a follow-up to the Galileo mission that yielded strong evidence that Europa is harbouring an ocean beneath a frozen crust of unknown thickness.
Europa is around the same size as Earth’s moon and if it is concealing an icy sea under its crust, the body could have more than twice as much water as Earth. With abundant salt water, a rocky sea floor and the energy and chemistry from tidal heating, Europa could turn out to be the best place in the Solar System to look for alien life.
“Europa has tantalized us with its enigmatic icy surface and evidence of a vast ocean, following the amazing data from 11 flybys of the Galileo spacecraft over a decade ago and recent Hubble observations suggesting plumes of water shooting out from the moon,” said John Grunsfeld, associate administrator for NASA’s Science Mission Directorate, in a statement.
“We’re excited about the potential of this new mission and these instruments to unravel the mysteries of Europa in our quest to find evidence of life beyond Earth.”
President Barack Obama and NASA announced the mission to Europa as a priority back in February, because it’s seen by many astrobiologists as the best place to look for life beyond Earth. The agency’s fiscal year 2016 budget included a request for $30m to develop a new spacecraft visit to the icy moon.
The plan is to send a solar-powered satellite into a long, looping orbit around Jupiter in order to get in repeated close flybys of Europa over a three-year period. NASA hopes to complete 45 flybys at altitudes ranging from just 16 miles to 1,700 miles.
The newly selected science instruments include cameras and spectrometers to produce high-res images of Europa’s surface that will help scientists to figure out its composition. An ice-penetrating radar will determine the thickness of the moon’s icy crust and search for subsurface lakes like those found beneath Antarctica. And the mission will also carry a magnetometer to measure the strength and direction of the moon’s magnetic field, which will allow researchers to work out the depth and salinity of its ocean.
NASA’s Hubble Space Telescope detected water vapour above the south polar region of Europa in 2012, so the mission will also include instruments to try to verify the observations. A thermal instrument will search Europa’s frozen surface for recent eruptions of warmer water, while other instruments will search for evidence of water and tiny particles in the moon’s thin atmosphere.
“The role E-THEMIS plays in the mission is to act as a heat detector,” explained Philip Christensen of Arizona State University, the principal investigator for the new Europa Thermal Emission Imaging System (E-THEMIS). “It will scan the surface of Europa at high resolution for warm spots.”
If the mission can confirm the plumes’ existence – and show they’re linked to a subsurface ocean – that will help scientists to figure out the chemical composition of the potentially habitable environment without need to drill down through the ice.
“ This is a giant step in our search for oases that could support life in our own celestial backyard ,” said Curt Niebur, Europa program scientist at NASA Headquarters. “We’re confident that this versatile set of science instruments will produce exciting discoveries on a much-anticipated mission.”
The nine instruments, listed in full here on NASA’s website, were chosen out of 33 proposals from researchers for the mission, which is scheduled to launch in the 2020s.
A tenth instrument, a combined neutral mass spectrometer and gas chromatograph proposed by Dr Mehdi Benna of NASA’s Goddard Space Flight Center, will be developed for other mission opportunities.