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astronomy news

The Moon Falls to Earth

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I’ve been out on a weeklong medical leave due to surgery and of course in my downtime a slew of cool astronomy events transpired. Most of you have read about Eris and Dysnomia now (the two latest solar system bodies to be named), so I won’t go into that, other than to say I think the naming is very, very clever.

What caught my eye in a pile of emailed press releases was a story about a rock found in Antarctica. You can see a large-size image of it here.

It’s a lunar meteorite, meaning it’s a rock from the Moon that fell to Earth, specifically in Antarctica. A group of researchers from Case Western Reserve University in Cleveland, Ohio, found it on December 11, 2005 on an icefield in the Transantarctic Mountains. They subsequently did some mineralogical testing on it to confirm its origin and announced their find last week.

Here’s a bit of info about the rock from the press release:

Scientists involved in classification of Antarctic finds at NASA’s Johnson Space Center and the Smithsonian Institution’s National Museum of Natural History said the mineralogy and texture of the meteorite are unusual. The new specimen is a very coarse-grained gabbro, similar in bulk composition to the basaltic lavas that fill the lunar maria, but its very large crystals suggest slow cooling deep within the Moon’s crust. In addition, the plagioclase feldspar has been completely converted to glass, or maskelynite, by extreme shock (presumably impact events). The new specimen most closely resembles another Antarctic meteorite, Asuka 881757, one of the oldest known lunar basalt samples.

Like the other lunar meteorites, MIL 05035 is a piece of the Moon that can be studied in detail in the laboratory, providing new specimens from a part of the lunar surface not sampled by the US Apollo program. Many researchers believe that Apollo visited some of the most unusual and geochemically anomalous regions of the Moon, and lunar meteorites, knocked off the surface of the Moon by random impacts, give us samples that are more representative of the Moon as a whole. The highly-shocked nature of MIL 05035 suggests an old age and may provide new constraints on the early intense bombardment of the Earth-Moon system, improving our understanding of the history of the Earth’s nearest neighbor and aiding NASA’s efforts toward a return to the Moon.

Following the existing protocols of the U.S. Antarctic meteorite program, scientists from around the world will be invited to request samples of the new specimen for their own detailed research. Details concerning initial characterization of the specimen and sample availability are available through the Antarctic Meteorite Newsletter, available on the Web at (http://curator.jsc.nasa.gov/curator/antmet/amn/amn.htm) and mailed to researchers worldwide.

Discovery of this meteorite occurred during the fourth full field season
of a cooperative effort by the National Science Foundation (NSF) and the National Aeronautics and Space Administration (NASA) to enhance recovery of rare meteorite types in Antarctica, in the hopes new martian samples would be found.

So, how do rocks from the Moon get to Earth? As you might have figured out from the press release segment, bombardments and collisions knock rocks off of one body and send then careening through space. Eventually, if orbits match, those rocks stray into Earth’s orbit and come to rest on our planet. Rocks from Mars have also made the trip, taking a little longer than rocks from the Moon. No matter where they come from, however, meteorites give us fascinating glimpses into their parent bodies and into their histories.

This rock appears to be evidence from early in the Moon’s formative period, when molten lavas were cooling deep beneath the surface. How this particular rock got blasted loose and sent on its way to Earth is a story waiting to be told. I suspect it will involve a massive impact and tremendous outbursts of rock from the Moon.

astronomy news, Astronomy outreach, IAU, Pluto

And Now, Cooler Heads Will Prevail…

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or Not…

It seems the hoo-hah over Pluto and the newly-voted-upon definitions of “planet” and “dwarf planet” and “plutonians” (which reminds me of a race of science-fictional beings with green antennae wiggling around on their heads) is hardly over. Oh, at first glance, as I mentioned in previous entries, it seemed like a good way to finally get some definitions that make sense and help us figure out how to categorize things in the solar system.

Unfortunately, the new definitions don’t always help. If you apply some of the “rules” described in my previous entry, you could end up with some pretty ludicrous outcomes. Take, for example, the idea that a planet has to have “swept its orbit clean” dynamically. What, exactly, does that mean? Well, when a solar system forms, the larger pieces get glommed together (the technical term is “agglomerate”) from smaller pieces. The bigger agglomerations attract or sweep up the smaller pieces. Eventually a planet (or planet-like entity) forms out of these sweepings, leaving surrounding space reasonably clear of the planetary birth leftovers. While this is an important step in the creation of a planet, I’m not so sure it should be given as much weight as it has been in the IAU definition that was approved.

But, when you apply this “a planet sweeps up its surroundings” rule, you could get in trouble. Let’s say you discover a star that has a bunch of planets around it, and there’s one the size of Jupiter in the collection. Great, sounds like a planet, right? But, what if it’s surrounded by a huge ring of debris, larger than Saturn’s, and clearly the “stuff” hasn’t been swept up by the planet—yet. By strictly applying the definition, if it hasn’t cleaned up its environment, that bad boy ain’t a planet.

Of course, there’s the whole issue of whether that Jupiter-sized thing is in hydrostatic equilibrium and “roundish.” So, right there you have conflicting reasons to call it a planet—or not.

That’s just one example. People are discussing this whole thing. Planetary scientists like David Jewitt of the Institute for Astronomy in Hawai’i, are commenting on their web pages and publicly about the ramifications of the defnitions. More are coming up with other examples that provide tests of the system, and in some cases, point out how silly parts of the system are. Right there, it looks like cooler heads need to prevail over the small percentage of astronomers who took matters into their own hands at IAU and summarily rewrote definitions on the fly. Will cooler heads prevail? Good question, but in the meantime, we have been privileged to see “astronomers behaving badly” at the IAU (in the words of one of the attendees who was there for the discussion sessions and the vote). I think there’s some great street theater occurring in astronomy and planetary science circles, and that means this thing ain’t over yet.

Already there is a petition going around among some really well-known and respected planetary scientists denouncing the whole contretemps at IAU and refusing to use the new definitions. It may gather lots of steam, and that steam may come to a rather explosive head at the next IAU general congress in 2009.

Still, dissent means we should get a much better definition. And, as I keep saying, this can only serve to strengthen the science we do, and keep reminding us that the scientific process is not one of arbitrary standards and wishful thinking, no matter how badly some astronomers may behave at any given time.

Speaking of astronomers behaving badly, I am reading a really good book right now called Stargazer: The Life and Times of the Telescope. It’s written by Fred Watson, who is the astronomer-in-charge at Anglo-Australian Telescope in Siding Spring, Australia. Fred gave a talk at the International Planetarium Society meeting in Melbourne last month titled “Astronomers Behaving Badly,” in which he detailed some of the astronomical hijinks of past astronomers. He also explains these in great and amusing detail in his book. You also get a nice little introduction to the development of the telescope, which is sort of the whole point of the book. I wonder what Fred will write (providing he’s still around) in some future decade about the astronomer hijinks over Pluto?