September 29, 2012 | David F. Coppedge

Planets and Moons Beneath the Surface

Can science peel back the surfaces of objects to see what’s underneath?  Can they go under the observations to find the explanations?

Investigating Vesta:  The $466 million DAWN spacecraft left asteroid Vesta recently after a year in orbit, and is now on its way to the largest asteroid, Ceres.  Two surprises were shared on the news recently: (1) Vesta is “surprisingly covered in hydrogen,” reported  (2) “Surprising troughs” belting the equator might have resulted from a collision.  One theory says that the troughs, “a puzzling finding,” that resemble earth grabens (sunken valleys between faults), resulted from a collision – but only if Vesta has a differentiated interior.  Another theory suggests a collision that caused the south pole crater may have spun the equator so fast it bulged.    Either way, the troughs are phenomenal: longer than the Grand Canyon and three times as deep.

Timing Titan:  More “surprising” news comes from Saturn’s large moon Titan, reported Science Daily.   Now that we have data from an entire Titan year (29.5 years, counting data from Voyagers 1-2 and Cassini), we can see seasonal changes occurring.  “Dr Athena Coustenis from the Paris-Meudon Observatory in France has analysed data gathered over this time and has found that the changing seasons of Titan affect it more than previously thought.”  Said changes are primarily atmospheric, though.  The article mentioned the continuous ethane production from solar radiation but did not get into the time problem this creates (2/09/2011).  Coustenis did not elaborate on why Titan is interesting to study because of “astrobiology” even though no life is found there.

Europe on Europa:  A European scientist has concluded that if Europa has an ocean under its ice, it is deeper down than thought.  “Missions hoping to explore the huge subsurface ocean thought to exist on Jupiter’s moon Europa may have to dig deep — really deep, said, like 25-50 kilometers instead of just a few miles as previously hoped.  “There could be areas of liquid water at much shallower depths, say around 5 kilometers, but these would only exist for a few tens of thousands of years before migrating downwards,” the French Czech said.  This would put the quash on mission plans to dig down to the water, where the life presumably is.

The Martian water war:  Opinions are still swinging between a wet Mars and a dry Mars even after the revelation that many of the lakes or gullies were likely caused by volcanoes (see 9/11/2011).  The MSL Curiosity Rover has just taken a stunning picture of conglomerate and gravel that seems diagnostic of flowing surface water from sometime in the past, at least on an alluvial fan in Gale Crater.  JPL rushed the photo in a press release because of its significance on Sept. 27.  “Bingo!Science Magazine responded.  But New Scientist held open the possibility that fluids other than water could have deposited the gravels.  When did the water flow, if it did?  “We think what we’re looking at is several billion years old,” Bill Dietrich said, who calculated the flow of water that might have produced the deposits. “How to get better than that, I don’t know. This is a common discussion point.”   The very next day, though, Science Daily reported on findings that show that Gale Crater may be “drier than expected.”   Water cannot exist on the surface now due to the low atmospheric pressure, one hundredth that on Earth.  If Mars ever had an atmosphere that allowed liquid water, it may have been lost by an atomic-level erosion from the solar wind called sputtering, PhysOrg reported.

The Martian EarthAstrobiology Magazine believes that analogous terrains on Earth (like the Atacama Desert of Chile and the salt pans of Tunisia) can help us understand processes on Mars.   Without water, oxygen and life, though, the differences may outweigh the similarities.

Messages from Mercury:  Curiosity is not limited to Mars; there’s some at Mercury, too, where since March 2011 MESSENGER is in orbit checking out the innermost planet.  NASA calls Mercury’s surface a “curiosity,” reported, because it is smoother than expected, “with less elevation than observed on volcanic Mars or the moon.”  Planetologists are “divining water ice,” the article continued, by looking for ice traps in permanently-shadowed craters at the poles.  For Mercury to maintain a magnetic field by an electric dynamo, theorists have to keep a molten core going, “since liquid cores are believed to generate magnetic fields.”

If you always keep in mind the difference between observation and divination, between empiricism and speculation, between discovery and explanation, you can still enjoy the space program.


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