Cubesats Payload on Europa Clipper Mission

Artist's impression of cubesats exploring Europa.

Credit: NASA/JPL-Caltech

NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif., has selected proposals from 10 universities to begin investigating the possible use of cubesats as auxiliary components to missions to Europa and beyond.

Cubesats are small, low cost space probes that can be used to collect scientific data by themselves or part of a “flock.”

They have been used extensively in the low-Earth orbit, providing a low-cost means for universities and institutions to carry out experiments in this microgravity environment.

As cubesat technology is maturing, so does the scope of their application.

So, as NASA steps up its plans for the Europa Clipper concept to visit the icy Jupiter moon, JPL has asked for cubesat proposals from universities that could complement the primary Clipper payload.

As we have a mission going to Europa, why not attach some cubesats for the ride?

NASA has outlined some key science objectives these axillary cubesats should be able to carry out, including “reconnaissance for future landing sites, gravity fields, magnetic fields, atmospheric and plume science, and radiation measurements.”

“We’ve seen some innovative and quite creative surprises among the CubeSat ideas submitted by these universities,” said Barry Goldstein, pre-project manager for the Europa Clipper mission.

“Using CubeSats for planetary exploration is just now becoming possible, so we want to explore how a future mission to Europa might take advantage of them.”

The chosen proposals have been awarded $25,000 each to develop their cubesat concepts to be included in the study, which is expected in the summer of 2015.

Europa is known to possess a sub-surface ocean of liquid water protected by a thick icy shell. As we learn more and more about this little world, our fascination with its life-giving potential is only amplified.

We now know that, combined with the oceans of water, nutrients are actively cycling to and from the surface. The icy surface appears to have plate tectonics.

Also, scientists believe there’s an abundance of oxygen in the ocean that’s heated by the tidal squishing of Europa’s orbit around Jupiter.

All of these factors point to a possibly habitable world where it has been hypothesized that multicellular life could thrive, but to test this hypothesis, we need to start sending missions to Europa so a close-up picture of its life-giving potential may be formulated, a mission that could be accelerated by the introduction of hitchhiking cubesats to the next big NASA missions to Jovian orbit.

Giant Geysers Mysteriously Disappear on Jupiter's ice-covered moon Europa

This artist's concept image depicts a water vapour geyser erupting from the surface of Jupiter's icy moon Europa.

Credit: NASA/ESA/K. Retherford/SWRI

The huge plumes of water vapour erupting from Jupiter's ice-covered moon Europa seem to have vanished, and scientists aren't sure why.

In December 2013, researchers using NASA's Hubble Space Telescope announced that they had spotted evidence of geysers blasting into space from Europa's south polar region.

The discovery sparked a great deal of excitement among space scientists, as it suggested that a robotic flyby probe might be able to sample Europa's subsurface ocean of liquid water without even touching down.

However, follow-up Hubble observations in January and February of this year showed no signs of the plumes, which were estimated to reach about 125 miles (200 kilometers) into space.



There are several possible explanations, researchers said. For example, Europa's geysers may be sporadic, more like volcanoes here on Earth than the plumes blasting pretty much constantly from the south pole of Saturn's icy moon Enceladus, which harbours a subsurface ocean like Europa.

It's also possible that Europa's plumes are only visible to Hubble's instruments at certain times.

"It could be just the way that we use the auroral emissions coming from those plumes at the UV [ultraviolet] wavelengths of light that we use with Hubble," discovery team member Kurt Retherford, of the Southwest Research Institute in San Antonio, told reporters.

"These things depend on Jupiter's plasma environment," Retherford added.

"Maybe there were just a lot of particles, atoms, getting excited by electrons and ions in Europa's atmosphere, more so than at other times, and [they] just lit up the plumes more than they usually do."

Further, the plumes may sometimes simply be too small to see, Retherford said. (Enceladus' geysers have been observed relatively close-up by NASA's Saturn-orbiting Cassini spacecraft, but scientists are relying on the Earth-orbiting Hubble to study the features on Europa.)

This NASA image shows the location of water plumes on Jupiter's icy moon Europa as seen by NASA's Hubble Space Telescope in December 2012. 

The discovery marked the first time strong evidence of water geysers on Europa.

Credit: NASA/ESA/L. Roth/SWRI/University of Cologne

Another possibility is that the geysers don't exist, that the detection by Hubble, which was based primarily on observations the telescope made in December 2012, was an artifact or misinterpretation of some sort but Retherford stressed that this is unlikely.

"The best explanation still is plumes for that dataset, no doubt about it," he said.

Retherford and his colleagues are going to look for the plumes again soon. They'll train Hubble on Europa from November through April, in a more comprehensive attempt to confirm the existence of the water-vapour geysers and to characterise their behaviour.

"The question is the variability aspect of the plumes. Why do we see them in some observation sets and not others?" Retherford said.



Learning more about the plumes is a key priority for astrobiologists and for NASA, which is eyeing a mission to Europa in the mid-2020s.

The leading candidate for that mission at the moment is probably a probe called the Europa Clipper, which would make multiple flybys of the icy satellite.

"This is the kind of thing that could have a profound impact on how we explore Europa," Curt Niebur, outer planets program scientist at NASA headquarters, said during a NASA planetary sciences subcommittee meeting Wednesday (Sept. 3).

"With an ocean that is tens of kilometers below the ice, most likely, if you can have a plume that's possibly bringing material from that ocean up to orbit, well, that's going to affect how you explore," Niebur added.