Oct. 2003 Asteroid/Comet/Meteor News

3 October 2003

The Heber Springs, Arkansas Sun-Times had an Oct. 3rd article, "Local recalls falling of Miller Meteorite." The fall was witnessed on 13 July 1930, and the meteorite, weighing 13.7 kg. (36.6 lbs.), landed "about fifty yards" from an occupied house in what is now Greers Ferry in north-central Arkansas. "1930 Arkansas" may ring a bell, since A/CC told earlier about another, larger meteorite that fell about 80 miles (130 km.) away, near a house in the state's northeastern corner on February 17th of the same year. The Miller Meteorite is now in the collection of the American Museum of Natural History (AMNH) in New York City.

The Minor Planet Center updated its Discovery Circumstances pages on Oct. 8th with namings for 69 LINEAR-discovered asteroids, from 19550 Samabates (1999 JP61) to 19835 Zreda (2000 SQ252). No new numberings were issued for asteroids, but the Periodic Comet Numbers page was updated with 1978 C2=2003 T1 newly numbered as 157P/Tritton.
      The previous namings and numberings came on Sept. 12th.

Spacewatch has a new FMO Project to involve the public in observing runs with its 0.9 telescope by having them watch for fast-moving objects (FMOs) that cannot be easily or reliably detected by software automation. Discovery and recovery credits will be given. "The only requirements for participation in the FMO project are 1) interest, 2) sharp eyes and 3) access to a computer during the hours that the Spacewatch mosaic system [CCD camera] is in operation." A broadband Internet connection is recommended, along with 1280x1024 screen resolution and a 19" monitor. "Knowledge about astronomy" is "Useful (but not necessary)." The site includes a tutorial that should be interesting even for those who don't participate, and further help is available for those who do.

The big question     (8 October 2003)

After more than three weeks of news about bolides seen around the globe and about tiny globe-buzzing asteroids, the big question is, Has Earth encountered some kind of minor object stream? It has even been suggested that all this activity could be associated with fireballs seen last September and October, as if Earth is on its second pass through a field of space boulders. In regard to just two events separated by a few hours, one over California and another over Europe, a San Jose Mercury article of September 30th quoted Peter Jenniskens, who studies such streams for NASA, as saying "maybe we have a bit of a shower of bright fireballs going on at the moment."
      Space.com, in its October 6th article about tiny 2003 SQ222, quotes Clark Chapman as saying it is hard to see how there could be a connection between events separated by hours, "let alone things that are happening over the course of a week or two. But . . . there have been a lot of these reports. . .  So who knows?" And he told Space.com incidentally that "about a week ago, my wife and I saw a gigantic bolide." (If that was seen over Colorado, it hasn't yet been reported on Chris Peterson's Fireballs page as of last check.)
      One reason for so many recent tiny asteroid discoveries is that observatory hardware and techniques are becoming ever better at discovering small fast-moving objects, and there are a lot to discover. The Space.com article reports from Alan Harris that an estimated 3,000 asteroids pass between the Earth and Moon every year, and "Perhaps 100 of them come closer than 2003 SQ222."
      It is very human for people to try to find a pattern in poorly understood natural events. But, thanks to the Web and an increased public awareness and interest, it could be that witnesses and the news media are just doing a better job of telling the world about local experiences of a randomly scattered but overall constant phenomenon.
      There is, however, also this: A report last November about large atmospheric events, "The flux of small near-Earth objects colliding with the Earth," was widely hailed as lowering estimated impact risks (see A/CC news links). But lead author Peter Brown also issued some big caveats, such as: "a key uncertainty remains, says Brown: whether large and dangerous meteors are concentrated in streams" (New Scientist), and "Based on past observations, it seems likely there is also a non-random component to the impact flux at these smaller sizes which would suggest our estimates are lower bounds to the true impact risk" (UWO news release).

On Oct. 23rd, MPEC 2003-U55 announced 2003 UC20 as discovered by LINEAR on the 21st and followed up on the 22nd by LINEAR with Table Mountain and Tenagra II observatories, and on the morning of the 23rd by Table Mountain. From its brightness (H=19.3), 2003 UC20 was estimated to be on the order of 475 meters/yards wide.
      With the MPEC was this copyrighted note from Timothy Spahr:

“ The orbital elements for 2003 UC20 bear some resemblance to those of 1954 XA. Attempts to link the two apparitions have not been successful, although a number of dynamical routes that allow 2003 UC20 to make a close Earth approach in 1954 have been identified. Further observations are very desirable. ”

SOHO ends public participation

After about 650 discoveries, with some 100 still unreported to the IAU, SOHO comet hunting has now come to a halt. Derek Hammer, the last of the ESA/NASA mission staff members who used to confirm, measure, and report discoveries to the Minor Planet Center (MPC), on August 4th posted his final message to the SOHO-hosted chat page for announcing and confirming SOHO comet discoveries.
      Most of the comets discovered via SOHO were on a final dive into the Sun, a type of cometary phenomenon that was almost unknown before SOHO. Some discoveries were "sungrazers," and a few were ordinary comets.
      NASA and ESA have let die a low-budget effort that involved citizens worldwide in doing real science and that resulted in some very nice PR about stunning discoveries and public participation in an international space mission via the Internet. This ends not only future science results but also hard-won results that hadn't finished processing. The last MPEC with SOHO discoveries was 2003-P02 of August 1st, and the German Comet Section reported the next day that "nearly 80 Kreutz comets" were yet to be put through to the MPC. Tony Hoffman says "nearly all the Kreutz comets found since late November, 2002" remain unprocessed. Maik Meyer's backlog page puts this Kreutz family number at "close to 100 comets," and also lists five uncataloged non-Kreutz comets.
      Many small dead comets may seem unimportant relative to "'real' astronomy," budget constraints, and the success of big-ticket public outreach efforts that were planned instead of self-evolved, but a hundred comets (and more with time) out of some 650 is a very large percentage of the data potentially available to help better understand the nature and origin of the large Earth-crossing comets from which it is believed these last shards came. The previous data is still there to be processed, and the images are still coming in from SOHO and being archived, but it is unknown what it will take to make any of this be useful to minor object science.
      Update: SOHO resumed support two months later for public participation, as A/CC reported Dec. 26th.