Trending: Moons With Oceans

Europa has one. Enceladus has one. Titan might have one. Now, it seems every moon wants an ocean under its crust.

Europa was one of the first to boast of an ocean under its ice. Now that vapor plumes have been confirmed by Hubble, the icy moon of Jupiter joins Saturn’s moon Enceladus as a Yellowstone Park of sorts. With the explosion of water from deep down, can hydrobioscopy be far behind? David Rothery (The Open University) writes for The Conversation, “New water plumes from Jupiter’s moon Europa raise hopes of detecting microbial life.” [Note to reader: no life has been detected.] Rothery doesn’t ask, predictably, how long this eruptive process could be going on. Nor does Alexandra Witze at Nature, who is more interested in the suggestion that “Watery jets could be tapping into a buried ocean with the potential to support life.” Ditto for Astrobiology Magazine and its update. Images of the telltale vapor plumes were posted on Space.com.

The newcomer to the ocean club is Saturn’s medium-size moon Dione. Science Daily says that a study from Belgium proposes an ocean 100 miles below the moon’s icy crust. That’s a lot farther down than the one presumed under Enceladus. The “club of ocean worlds” is growing with each new mission to the outer solar system, the article says. That club is coextensive with the hydrobioscopy club:

Dione’s ocean has probably survived for the whole history of the moon, and thus offers a long-lived habitable zone for microbial life. “The contact between the ocean and the rocky core is crucial,” said Attilio Rivoldini, co-author of the study. “Rock-water interactions provide key nutrients and a source of energy, both being essential ingredients for life.” The ocean of Dione seems to be too deep for easy access, but Enceladus as well as Jupiter’s moon Europa are generous enough to eject water samples in space, ready to be picked up by a passing spacecraft.

Illustra’s new film Origin mentions a few more requirements for life than just matter and energy.

“Wait for me!” Pluto cries to the club of ocean worlds. Astrobiology Magazine shouts, “Pluto’s ‘heart’ sheds light on a possible buried ocean.” A new study from New Horizons Spacecraft data “finds a high likelihood that there’s more than 100 kilometers of liquid water beneath Pluto’s surface” with a high salt content similar to the Dead Sea. Scientists don’t actually detect water itself, but infer it from density measurements and orbital mechanics. The peculiar heart shape of Pluto’s Sputnik Planum tantalizes theorists with images of an impact puncturing the ocean, allowing slushy material to well up into the crater. In this case, though, they’re not mentioning life.

The scenario that best reconstructed Sputnik Planum’s observed size depth, while also producing a crater with compensated mass, was one in which Pluto has an ocean layer more than 100 kilometers thick, with a salinity of around 30 percent.

“What this tells us is that if Sputnik Planum is indeed a positive mass anomaly —and it appears as though it is — this ocean layer of at least 100 kilometers has to be there,” Johnson said. “It’s pretty amazing to me that you have this body so far out in the solar system that still may have liquid water.”

Back at Enceladus, geysers are erupting water out the rifts at the rate of a few hundred kilograms per second, a new study at Icarus claims. At one flyby, the data supports 900 kilograms per second, about half a ton per second, 30 tons per minute, 1,800 tons per hour, 43,000 tons per Earth day. Could that much material come out of this little moon for billions of years? Quick: someone do the math.

Bodies without oceans can take some comfort by other kinds of activity. Astrobiology Magazine says, “The Incredible Shrinking Mercury is Active After All.” The activity is the buckling of fault scarps as the planet cools. Some of the scarps appear “geologically young,” the scientists say. “The young age of the small scarps means that Mercury joins Earth as a tectonically active planet, with new faults likely forming today as Mercury’s interior continues to cool and the planet contracts.”

“This is why we explore,” said NASA Planetary Science Director Jim Green at Headquarters in Washington, D.C. “For years, scientists believed that Mercury’s tectonic activity was in the distant past. It’s exciting to consider that this small planet – not much larger than Earth’s moon – is active even today.”

Icarus announced the presence of volatile ices on Mercury locked in cold traps that never see sunlight, but warned that they are not protected from magnetospheric charged particles, galactic cosmic rays and solar energetic particles. What happens when the delicate ices are hit with this energy?

This focused radiation will initiate chemistry that may create dark compounds that could be the dark low-albedo materials observed by MESSENGER instruments. Thick layers will be created by radiolysis and chemistry as well as gardening, overturn, sputtering and other physical processes occurring simultaneously.

Some of that activity is evident in the “planet’s weird surface” features, Space.com says, where young-looking terrain sits alongside heavily cratered regions. The origin of Mercury is still in dispute. In “How Was Mercury Formed?” Space.com contributor Nola Taylor Redd gives it her best shot, investigating three contradictory models, ending with a shooting-gallery model of violent collisions with one big blow that made Mercury what it is today – if you like war stories.

“The larger objects now tend to scatter the smaller ones more than the smaller ones scatter them back, so the smaller ones end up getting scattered out of the pebble disk,” study co-author Katherine Kretke, also from SwRI, told Space.com. “The bigger guy basically bullies the smaller one so they can eat all the pebbles themselves, and they can continue to grow up to form the cores of the giant planets.”

Every good space tale leaves enough gaps in the scenario to keep the scientists gainfully employed.

The gaps help keep the cycle going. Materialist scientists feed stories to the teachers, who inspire the children to imagine deep oceans swimming with weird alien creatures. The children grow up to become material scientists.  Round and round it goes. Everyone’s happy except the planets, who say, “Hey, I’m dead.”