Surprising Youth in the Solar System

Four solar system objects in the news look young, not billions of years old.

Pluto: It’s officially published in peer-reviewed literature: the surface of Sputnik Planum on Pluto cannot be more than 10 million years old (see PLoS One preprint on arXiv.org). Planetary scientist David Trilling from Northern Arizona University. “There have been lots of press releases describing various aspects of Sputnik Planum, but, as far as I know, this is the first time that the age estimate of 10 million years or younger appears in the peer-reviewed literature,” he said in an email to Discovery News (quoted by Space.com).* 10 million years sounds like a lot, but it’s only 1/450th the assumed age of the solar system. How did Trilling come up with his age estimate? “What I did was take the pictures that we have seen — the amazing pictures! — and calculate, based on Pluto’s orbital environment, what the impact rate and therefore the surface age of Sputnik Planum must be,” he said. Elizabeth Howell writes, “There’s a lack of craters on its surface, making it a unique area on Pluto and a rare spot in the solar system — it turns out it could be very young terrain indeed.” The article goes on to postulate 3 ways the surface might have been rejuvenated: (1) relaxation of nitrogen ice, erasing the craters; (2) ice on the bottom rising to the top (the lava lamp theory); (3) “The ice could be partially melted at its bottom and from time to time, erupt on to the surface as cryo-lava.” Each of these ideas, though, would have to explain how such processes could be ongoing for billions of years on a world that should be frozen and geologically dead.

Pluto Volcano: Also in the news, Space.com published more information about Pluto’s “huge” ice volcano named Wright Mons. It’s the largest such feature in the solar system, but on one of the smallest of planets—and it may still be active. The article begins, “Pluto’s weirdly dynamic and ‘young’ surface has just become even more intriguing with the release of this stunning color image of what is thought to be a huge cryovolcano, or ice volcano.” Scientists did not predict this.

As the dwarf planet is so far away from the sun, it was assumed, before the historic New Horizons Pluto flyby in July, that it would be a frozen, static and crater-filled world. But as observations by the NASA spacecraft are showing us, Pluto has an astonishing impact crater-less surface, with some regions dominated by dynamical atmospheric and surface processes….

Now, with the discovery of this 2.5 mile-high mountain on Pluto’s surface, planetary scientists are trying to understand how the 90 miles-wide feature formed and whether it could be yet another sign of the small world’s surprising dynamism and a striking example of cryovolcanism….

This tells us that if it really is an ice volcano, it had to have been active in recent geological history — if it was an inactive, static artifact, it should be peppered with impact craters. Instead, it appears recently active processes — possibly related to Pluto’s ice — have eroded most of the impact craters away.

In short, Pluto is telling us a story through its surprisingly active geologic processes, processes that few scientists would have bet on existing in the outermost reaches of the solar system before New Horizons’ dwarf planet encounter.

Enceladus: A photo of the “dalmatian terrain” on Enceladus suggests youth, too. Astrobiology Magazine shows the terrain, which suggests bedrock falling down a slope or sitting atop a hogback ridge. “On Enceladus, with no wind to scour loose particulate ice or ‘snow’ off of them, the solid blocks are probably cleared by some combination of downslope movement of particulates, and perhaps sublimation,” the article suggests, but if so, it must have happened relatively recently due to the lack of craters. A new paper in Icarus calculates a suggested heat source from obliquity (tilt) of Saturn’s little geyser moon, but does not find it sufficient to account for the geysers: “Obliquity tides are unlikely to be the source of Enceladus geological activity.”

Comet 67P: Astrobiology Magazine posted a beautifully detailed image of the Imhotep region on Comet 67P showing boulders, dusty terrain and signs of erosion. The Rosetta orbiter has detected water ice on the surface of Comet 67P in two separate 1-meter patches, Space.com reports. “Both patches are associated with cliff walls and recent debris falls, which likely explains why the ice did not quickly boil away into space,” the article postulates. Movement of surface material is expected as the comet swings around the sun and creates the comet tail, but every comet must eventually burn out and lose all its volatiles. Over hundreds of orbits, the volatiles should disappear from the upper layers; only refractory (rocky) material should remain on the exterior. PhysOrg quotes a planetary scientist not sure about how to react. “First, not finding ice was a surprise; now, finding it is a surprise.” It is indeed surprising to find water ice on the surface of a body with the density of cotton candy.

Asteroid Ceres: Speaking of water, “Bright spots on Ceres may contain water,” Science Magazine announces. Water could not remain long on an airless surface without sublimating unless uncovered recently by impacts. It’s vanishing: “One crater called Occator fills with a haze each day, which disappears at night, probably caused by clouds of evaporated water.”  In addition, Astrobiology Magazine posted images of a young crater named Kupalo that reveals “bright material exposed on its rim, which could be salts, and its flat floor likely formed from impact melt and debris.” It’s not alone in its youth. “One of the youngest large craters on Earth’s moon, called Tycho, has similar fractures.” Another crater named Dante has bright spots, like Occator. Did the planetary scientists predict any of this?

“When we set sail for Ceres upon completing our Vesta exploration, we expected to be surprised by what we found on our next stop. Ceres did not disappoint,” said Chris Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles. “Everywhere we look in these new low- altitude observations, we see amazing landforms that speak to the unique character of this most amazing world.”

*Setting an upper limit does not mean the surface is 10 million years old. It only means it cannot be older. It would be like placing the upper limit on your lifetime as 969 years, the age of Methuselah.

So many of these surprises would vanish if scientists kicked some A.S.S. and thought outside the moyboy paradigm. If it looks young, let it be young! They won’t ever consider that, we know, because Charlie, their idol, needs lots of time for Tinker Bell do her evolutionary magic on Earth.

Instead of repenting for their failures, the planetary scientists dream on. They want to spend a billion dollars on a mission to Enceladus or Titan to look for life, Space.com reports. The hydrobioscopy habit is hard to break, and we taxpayers have to fund their addiction.