Mercury, Moon May Still Be Erupting
Two objects that should be cold and dead show surprising volcanic activity. Other indications of youthfulness in the solar system are noted.
Mercury
Astrobiology Magazine published new findings from the MESSENGER spacecraft at Mercury that suggest recent—and perhaps ongoing—volcanism: “Volcanoes on Mercury may have been more explosive than previously anticipated, and they may have erupted more recently, as well.” This is not supposed to be. If the planet is 4.5 billion years old (the conventional age of the solar system), it should have cooled to a hard ball eons ago. The article includes photos of bright areas indicative of recent, explosive eruptions. There’s no explanation given for these unexpected findings, which are surprising in at least three ways:
- Recent age: “Scientists examining volcanic deposits on the surface of the planet using NASA’s MESSENGER spacecraft found evidence of explosive activity as recently as a billion years ago. Previous studies of the cratering of other lava flows placed most volcanic activity at more than 3.5 billion years in the past.
- Quantity of volatiles in the lava: “scientists think that an impact early in the planet’s lifetime evaporated most of the crust, vaporizing most of its volatile components. ‘So the presence of explosive volcanism on Mercury is a little bit surprising,’ [Laura] Kerber [JPL] said.”
- Similarity to Earth’s moon: “In fact, volcanism on the hot planet bears a strong similarity to volcanism on the Moon, which scientists say is surprising because of their differences. ‘Both Mercury and the Moon are a lot smaller than the Earth, and so will have cooled more than Earth since their formation. For that reason, a lot of models would not predict volcanism within the last two billion years,’ lead author Rebecca Thomas of The Open University, in the United Kingdom, told Astrobiology Magazine by email.
Breaking news: Water discovered on Mercury! Shadowed craters harbor several billion tons of water ice, BBC News reports. The “geologically young” ice deposits are “surprising,” Dr Nancy Chabot says; “The uniform surface texture of presumed water-ice areas in Prokofiev crater suggest the deposits arrived relatively recently.” The age is an issue:
She added: “One of the big questions we’ve been grappling with is ‘When did Mercury’s water ice deposits show up?’ Are they billions of years old, or were they emplaced only recently?
“Understanding the age of these deposits has implications for understanding the delivery of water to all the terrestrial planets, including Earth.“
Overall, the images indicate that Mercury’s polar deposits either were delivered to the planet recently or are regularly restored at the surface through an ongoing process.
If it’s an ongoing process, though, it would seem that water input must be balanced by water output. “One explanation could be that the deposits on Mercury are more recent,” the article says, otherwise a “considerable mass” of volatiles should have been delivered to the inner planets over billions of years. “This will be a very interesting line of inquiry going forward,” Chabot remarked. Francis Nimmo at UC Santa Cruz said in New Scientist, “It’s really hard to understand how an ocean could survive for billions of years inside something as small as Mimas.”
Moon
In a separate article, Science Magazine happened to mention “Recent volcanic eruptions on the moon“—so recent, in fact, that scientists cannot rule out ongoing activity. “The moon, thought to be cold and dead, is still alive and kicking—barely,” Eric Hand writes. “Scientists have found evidence for dozens of burps of volcanic activity, all within the past 100 million years—a mere blip on the geologic timescale. And they think that future eruptions are likely—although probably not within a human lifetime.” Once again, this is not supposed to be possible “For a world thought to have gone cold long ago,” because the smaller the body, the faster it cools.
Lunar scientists cannot ignore the anomalies any more. A map in the article pinpoints dozens of features that appear to show recent volcanic origin. Using crater count dating (see 5/22/12), they estimate some of these are 100 million years old, but even granting that age puts planetary science in a quandary: that’s only 2.2% of the assumed age of the moon. It should have been quiet by ten times that age (1 billion years). One feature is estimated to be 18 million years old, but that’s moot if the moon is still active and could erupt in the future. The only explanations are mere suggestions: (1) there might be more radioactivity in the maria, and (2) internal heat tends to leak out in “fits and starts.” Why either of those should be true is not apparent.
“Young volcanism indicates possibly more magma, or magma at higher temperatures, or magma at shallower depths, or all of the above,” said one expert quoted by New Scientist. “This paper demonstrates how much we don’t know about the moon,” said another. The two explanations offered “both suggest the moon isn’t dead.” New Scientist wrote about this again on October 12, saying, “Lunar volcanoes suggest the moon may still be warm.” Reporter Maggie McKee quipped, “The man in the moon may still have some fire in his belly.”
Saturn
“Ring rain” is the phenomenon of water from Saturn’s rings raining down on the planet. A new estimate announced in the planetary science journal Icarus puts the the rate at almost a million billion trillion water molecules per second (1.0 to 6.7 x 1026 sec-1) being lost from the rings to the atmosphere. How long could this persist? The Abstract doesn’t say.
A new photo of the North Polar Hexagon was publicized by Space.com. This amazingly geometric figure, 20,000 miles across, filled with hurricanes larger than those on Earth, has persisted for over 30 years since first discovered in 1981 by the Voyager spacecraft. A video clip shows the “puzzling” hexagonal cloud changing over time but maintaining its geometric shape.
Mimas
Breaking News: Cassini scientists think Mimas may have a subsurface ocean—at least that’s the last unfalsified hypothesis from measurements of its orbital wobbles (National Geographic). If so, age becomes a serious problem, Eric Hand reports for Science Magazine: Mimas is “too small to have enough heat-producing radioactive elements in a rocky core to maintain a liquid ocean.” Proposing a subsurface ocean led another astronomer to have fits:
But not for very long, says William McKinnon, a planetary scientist at Washington University in St. Louis. If such an ocean were buried there, its tides would iron out Mimas’s orbital eccentricity within a few million years—eliminating the very thing that can keep the ocean liquid. That means that Cassini would have to be catching Mimas at an incredibly coincidental moment in its history, just after something put the moon into an eccentric orbit that in turn heated up and created the ocean. “I find it quite implausible,” McKinnon says.
Titan
Cassini scientists have watched with interest an ephemeral island appear and disappear in one of Titan’s northern hydrocarbon lakes (JPL press release). Steve Wall said, “Science loves a mystery, and with this enigmatic feature, we have a thrilling example of ongoing change on Titan.”
The press quickly latched onto reports of a cold cloud of cyanide (HCN) hovering over Titan’s south pole (see Space.com, Astrobiology Magazine, Nature Perspective, and original paper in Nature). One scientist quoted in Nature News said, “This is telling us that you have to expect the unexpected, even on ‘planets’ that we thought we knew relatively well.”
A separate paper in Icarus about Titan’s atmospheric tholins confesses, “The chemistry in Titan’s atmosphere and its resulting chemical structures are still not fully understood in spite of a great many efforts being made.”
Comets
Jupiter-family comets are disrupting rapidly, another paper in Icarus estimates. A “large percentage,” Michael J. S. Belton writes, “must physically disrupt, i.e., macroscopically disintegrate, within their median dynamical lifetime.” How quickly does this occur? “The typical disruption rate for a 1 km radius active nucleus is ∼5 × 10−5 disruptions/year and the dormancy rate is typically 3 times less,” he says. An average comet might disrupt within 25 to 100 years. “We also estimate that average fragmentation rates range from 0.01 to 0.04 events/year/comet, somewhat above the lower limit of 0.01 events/year/comet observed by Chen and Jewitt (Chen, J., Jewitt, D.C. [1994]. Icarus 108, 265–271).”
We are just weeks away from the Rosetta spacecraft’s historic landing of its lander Philae on the surface of comet 67P/Churyumov-Gerasimenko, scheduled for November 12. (Universe Today).
Asteroids
What happened to the Ceres family? It’s a murder mystery three scientists investigated in another paper in Icarus: “The case of the missing Ceres family.” This large asteroid should have kin: “Ceres is unusual among large (>250 km) asteroids in lacking a dynamical family,” the authors say; “We explore possible explanations, noting that its particularly large size and the ubiquity of families associated with other large asteroids makes avoidance of a sufficiently-sized collision by chance exceedingly unlikely.” Here’s their working hypothesis: “Because there seems to be no likely mechanism for removing a rocky Ceres family, and because the formation of a Ceres family of some kind seems nearly statistically inevitable, the lack of a Ceres family is indirect but independent evidence for Ceres’ differentiation.” Perhaps the upcoming orbital mission by the DAWN spacecraft next spring can shed light on this mystery.
Other main-belt asteroids undergo catastrophic disruptions, too. Another paper in Icarus begins, “We have calculated 90% confidence limits on the steady-state rate of catastrophic disruptions of main belt asteroids” based on observations of brightness variations. The new estimate: one catastrophic disruption per year for asteroids with absolute magnitude H > 28. Rotational disruptions, they say, occur 400 times as often. Impacts and spin are the main causes of disruptions. The paper did not mention new asteroids forming. How long before the main belt would be disrupted to fine dust?
Planetary scientists could avoid so many problems with their models if they would just abandon the A.S.S. (age of the solar system; see Darwin Dictionary). What is it that forces them to think in terms of billions of years? Clearly it’s not the evidence cited above. The number of anomalies are astronomical, yet they persist in clinging to that age figure. Why? You know the answer; it’s because Charlie needs the time for his evolutionary theory to work on Earth. So the Bald Assertions of Darwinism (B.A.D.) are the real reason for the B.A.D. A.S.S. position of secular planetary science.