Water Worlds Tempt with Life, Not Youth

More and more planets and moons are suspected of having liquid water, but what should be the logical implications?

Enceladus

The Arizona-sized moon of Saturn just got hotter. A press release from Jet Propulsion Laboratory announced that it may have hydrothermal vents as hot as boiling water deep underneath its icy crust. Not a single news report asked, “How long could this little moon stay so hot? Could it maintain this thermal activity for billions of years?”  Instead, they all were enticed by the “water = life” formula:

• Icy plumes bursting from Saturn’s moon Enceladus suggest it could harbour life (The Conversation)
• Hints of hot springs found on Saturnian moon: Particles streaming from Enceladus strengthen push to hunt for extraterrestrial life (Nature)
• Undersea Jacuzzi may give life to Saturn’s icy moon…boosts the chances of finding life snuggled below its cold exterior (New Scientist)
• Spacecraft Data Suggest Saturn Moon’s Ocean May Harbor Hydrothermal Activity… “The locations in our solar system where extreme environments occur in which life might exist may bring us closer to answering the question: are we alone in the universe.” (NASA Astrobiology Magazine)
• Researchers study methane-rich plumes from Saturn’s icy moon Enceladus… “This is highly suggestive of an Earth ocean analog, where early life formed in hydrothermal systems capable of producing methane.” (PhysOrg)

The original paper in Nature did not have this hydrobioscopy obsession, but neither did the authors address the age implications of this high temperature activity.  The focus was entirely on current mechanisms for maintaining water in a liquid state. Meanwhile, JPL (which manages the Cassini mission that gathered the data) quoted a NASA administrator who said, “The locations in our solar system where extreme environments occur in which life might exist may bring us closer to answering the question: are we alone in the universe.” The third of 3 highlights in the press release stated: “The results have important implications for the habitability of icy worlds.” That’s a wink, wink, nod, nod to reporters eager to prove Earth is not special, or that life can evolve anywhere where there is water.

Ganymede

Underground oceans are all the rage these days. The Hubble Telescope website announced new remote observations that suggest an underground ocean at Ganymede, Jupiter’s largest moon and the largest moon in the solar system. One cannot dig down and look, obviously; the ocean was inferred by observations of aurorae and how they wobble as the magnetic field changes. (Ganymede possesses a small magnetic field within Jupiter’s large magnetic field.) “By watching the rocking motion of the two aurorae, scientists were able to determine that a large amount of saltwater exists beneath Ganymede’s crust, affecting its magnetic field.” The ocean is estimated to be 95 miles down, and 60 miles thick. It would thus contain more water than all the Earth’s oceans combined, which are only 6 miles thick in places.

Once again, the press release held out the bait and reporters took it. “Identifying liquid water is crucial in the search for habitable worlds beyond Earth and for the search for life as we know it.” The same NASA administrator, John Grunsfield, held the fishing pole: “A deep ocean under the icy crust of Ganymede opens up further exciting possibilities for life beyond Earth.” Reporters quickly took the bait:

• The idea that a sub-surface ocean exists on Ganymede is exciting because wherever you have liquid water, you have one of the main ingredients for life. (BBC News)
• Scientists are particularly interested in learning more about watery worlds because life as we know it depends on water to thrive. (Space.com)
• Aurora reveals Jupiter moon’s secret subsurface sea… a technique that could also help in the hunt for alien life outside our solar system. (New Scientist)
• Confirmed: Jupiter’s moon Ganymede has a salty, underground ocean… Related: Enceladus may have ocean with right ingredients for life, scientists say… Related: how life could develop in the methane lakes of Saturn’s moon Titan. (L.A. Times)

Salty water is not going to help the life hunters; it wreaks havoc with cell membranes and many biochemical reactions. Even so, none of these articles discussed how Ganymede could retain water in a liquid form for 4.5 billion years—the assumed age of the solar system (A.S.S.).

Titan

Saturn’s large moon Titan doesn’t have liquid water on its surface or in its atmosphere, but that doesn’t stop reporters from speculating about life there also. (Want to see how an astronaut might survive on Titan? Look at this infographic from Space.com. It states, “Titan has no water, but some scientists wonder if life based on methane might live on Titan.” Also on Space.com, Joseph Castro speculated what it might be like to live on Titan or Enceladus, with its “potentially life-harboring ocean” deep under the ice.) Titan actually does have water in the form of ice, which is rock-hard at its surface temperature of -290° F.

Titan was in the news recently because of a new theory about its atmosphere. Reasonable calculations in the past had shown that the atmosphere could not survive for more than a fraction of the assumed age of the solar system. This has led to repeated attempts to find ways it could be replenished. The latest theory invokes gases escaping from under the crust (Astrobiology Magazine) via hydrothermal vents. Christopher Glein from the University of Toronto published his model in Icarus, basing his evidence on ratios of isotopes of noble gases; “Hydrothermal geochemistry can provide sufficient atmospheric methane and nitrogen,” he claims. To get it to work, he needs liquid water in the interior and transport to the surface. It will take a return mission to Titan to test his model, he says.  But it’s not just gas he has in mind. The Astrobiology Magazine article quotes him saying, that if water is down under, “This could set the stage for subsurface life.”

Not know:  A group at Cornell, including Mr. Titan himself, Jonathan Lunine, suggests that water is not even necessary to get “life ‘not as we know it’” at Titan. “Liquid water is a requirement for life on Earth. But in other, much colder worlds, life might exist beyond the bounds of water-based chemistry,” a Cornell press release begins. “…A planetary body awash with seas not of water, but of liquid methane, Titan could harbor methane-based, oxygen-free cells that metabolize, reproduce and do everything life on Earth does,” the article claims, calling this a “simultaneously imaginative and rigidly scientific view.” Lunine looks right proud of this speculation along with his grad student James Stevenson, who says he was inspired by the late atheist Isaac Asimov to think about “life not as we know it.” Again, it would take a probe to land in Titan’s methane lakes to test the model, so the speculative scenario is safe from falsification for a long time. Science Daily dutifully reproduced the imaginative article.

Earth’s Moon

What about our nearest neighbor? Don’t expect an ocean under its dry crust, but New Scientist ricocheted off evidence for explosive eruptions to the possibility of water down deep. China’s Jade Rabbit rover probed under the surface with ground-penetrating radar. It found volcanic evidence up to 400 meters down, suggesting explosive eruptions of lava. “For the eruptions to be explosive, a lot of gas must have formed,” the article says.  “The surface rocks don’t contain enough chemicals with low boiling points to make such explosive eruptions. This suggests there might be volatile molecules like water in the moon’s interior.” Space.com mentions “volatile contents” but not water specifically. Mike Wall’s headline reads, “The Moon’s History Is Surprisingly Complex, Chinese Rover Finds.” The most surprising findings, the rover scientists say, were that the eruptions included explosive pyroclastic rocks, and occurred late in the assumed lunar history. The rover ground to a halt in January 2014 with technical problems, after traveling 374 feet in two weeks. The composition of the ground it covered is “quite different” from the Apollo sites, Wall writes.

Water, Water Everywhere

The BBC News said of watery worlds, “Ganymede is just one of a large list of objects in the Solar System now thought to hide an ocean deep below the surface. These include the dwarf planets Pluto and Ceres; other Jupiter moons – Europa and Calisto [sic]; Saturn’s moons Enceladus, Titan and Mimas; and possibly Neptune’s moon, Triton.” Jim Green, NASA planetary science director, quipped: “The Solar System is now looking like a pretty soggy place.” You can have a lot of sog or fog without assuming it will produce a dog, hog, bog, log, or frog.

Update 3/17/15: The bright white spots the DAWN spacecraft sees on asteroid Ceres may be active eruptions (Nature, Science). They stand out like headlights from within a dark crater 80 km wide. When DAWN gets a closer look in April, we should know.

Whether engaging in hydrobioscopy or methanobioscopy, focusing on life from simple chemicals like H₂O and CH₄, or even higher molecules, is plain silly. Thank Jonathan Amos at the BBC for at least qualifying the water party with this line: “You need much more, of course – not least a source of energy and some complex carbon chemistry,” to which he should have added: a genetic code, hierarchical control systems, feedback from the environment, selectively permeable membranes, active transport, molecular machines, respiration, defense, reproduction, some kind of animating principle, and much more.

We’re used to the hydrobioscopy in secular papers. Not that it should be forgiven, but there’s another besetting sin illustrated in these articles: a complete blackout on the age issue. Enceladus cannot keep pumping out 15 gigawatts of eruptive power for billions of years. Mimas is even more surprising if it has an ocean, since there is no significant tidal pumping going on. Titan cannot maintain its atmosphere for billions of years. How convenient of Christopher Glein to hide it all under the crust, out of sight, out of testability; there’s no evidence of venting going on now.

The age issue should be front-burner on all these articles, but it’s as if a conspiracy of scientists has said, “DON’T mention the problem, lest creation sites hammer us with it.” Well, we noticed, and we’re hammering.