Falling Rocks Leave Holes in Science
Hard data in astronomy is hard to come by, except when it comes by special delivery – as with meteorites. If there is any class of phenomena that should be well understood, it should be space debris and the craters they form, because the processes involved can be watched in real time. Meteorites adorn many institutions and private collections. In addition to thousands of craters that can be studied on the moon and other bodies, we have plenty of examples right here on the home planet. The physics of crater formation is subject to modeling on computers. For good measure, experiments on crater formation can be performed in the lab by shooting materials into rock and ice. A few recent science reports illustrate, however, that a great deal remains puzzling and mysterious.
- What is it? National Geographic News reported that “A pair of mysterious meteorites discovered in Antarctica is baffling scientists who are struggling to determine the origin of the space rocks.” The rocks were “oddly rusted and salty and smelled like rotten eggs.” It’s not that they worry these were left by the Space Chicken; they just don’t know what laid them on the Antarctic ice. Unusual for meteorites, these two are partially melted and contain anomalous amounts of feldspar. “Thus there are two mysteries,” one of the discoverers said. “What is the parent planet for the rock, and what type of geologic activity on that planet produced the unusual mineral assemblage?” That seems to cover the most important points to know, other than that they exist.
- Low and behold: In Peru, eyewitnesses watched a crater form last September 15 when a large bolide hit the ground. The panic it caused among locals is of interest to psychologists, but the impact crater itself, now filled with water, is also filled with puzzles.
Space.com, the BBC News and Science Daily told how this crater is impacting ideas about meteorite fall and crater formation. Scientists were so baffled by it, some thought it was a fake: “It just didn’t make sense with what we understand of collisions with this type of fragile rock.” The object should have shattered and dispersed before hitting the ground. Bad news to humans dodging space rocks: this one appears to have hit with full force at 15,000 miles per hour.
The crater it formed (49 feet across) is leading some scientists to suspect other water-filled circular depressions around the earth might have formed the same way. One planetary scientist remarked, “Perhaps they also will defy our understanding.”
- Mercury falling: The MESSENGER team reported this week at the Lunar and Planetary Science conference in Boulder, Colorado that they can’t explain some mysterious craters. Space.com said that there are two new classes of craters in pictures from the January 14 flyby (see 01/17/2008) that “scientists are puzzling over how to explain.” Two craters have dark rims and another has an unusual shiny bottom. Of the latter, Clark Chapman remarked, “I haven’t heard any really convincing explanations from our science team. We don’t yet know what the material is, why it is so bright, or why it is localized in this particular crater.”
- Crater upheaval: Was it a salt dome? a circular monocline? a volcano, or something else? Long suspected to be an impact crater, Upheaval Dome in Utah is looking more like, indeed, it was hit by a space rock. Two Berliners reported in Geology this month that they have confirmed the impact hypothesis by detecting shocked quartz grains in the periphery of the central uplift. Calling this feature the “sphinx of geology,” they said, “The very controversial debate about Upheaval Dome’s origin has lasted nearly a century, over the course of which extremely different hypotheses (gradualism versus catastrophism) have been proposed.” Chalk one up for the catastrophists.
Space enthusiasts will surely want to peruse the craters that became visible yesterday during Cassini’s close flyby of Enceladus. Some of the craters in the north polar region (across the world from the geyser eruptions) appear semi-melted, while others are half-erased by subsequent geological activity. Others, with irregular edges, have large mounds in their centers criss-crossed by fractures. The lack of new impacts in the flows would suggest that these regions are very young.
Adding these stories to the upsets about crater count dating (12/20/2005, 06/08/2006, 05/14/2003, 12/27/2002) should convince onlookers that planetary scientists, like mountain drivers, also need to watch for falling rocks.
1. Buchner and Kenkmann, “Upheaval Dome, Utah, USA: Impact origin confirmed,” Geology, Volume 36, Issue 3 (March 2008), pp. 227-230.
The lesson of this entry is not that scientists are incapable of someday understanding this subject better. It is that here is a subject right under our noses that is poorly understood. If there are this many anomalies, upsets and mysteries about something easily amenable to scientific investigation, how reliable are their pronouncements about far distant and unobservable phenomena like dark matter, black holes and the birth of the universe?
Puzzles are good for science. Thank goodness there are plenty of mysteries for future scientists to solve. Let the reader of science news reports beware, however. Science reporters are among the most dogmatic in the world about accepted theories and consensus explanations. A little experience with puzzles and anomalies in science is an effective antidote for dupidity.*
* Dupidity, n. A tendency to become a dupe of the press. (A new CEH word coined for this occasion.)