The Asteroid/Comet Connection's
daily news journal about
asteroids, comets, and meteors

Today's issue status: done

• News briefs – planetary defense & prairie event
• Risk monitoring – NEODyS has posted 2004 FU4

Cover: Great Shefford Observatory on March 16th helped confirm 2004 ER21 (MPEC 2004-F16), which is seen here in Peter Birtwhistle's follow-up work late Saturday. This stack of 45 frames (20 seconds exposure each) is centered on the asteroid's motion, so stars appear as long streaks. For more about this and a dozen other H>22.0 objects discovered last week, see A/CC's "Small objects" report yesterday.

Planetary defense:  BBC has an item today, "Nasa considers impact alert plan." See also Space.com's report yesterday.

Prairie event:  The Saskatoon, Saskatchewan StarPhoenix has an article today, "Remnants of fireball may have landed in province." It reports that there are witness accounts from "as far south as North Dakota and north as La Ronge [and as far] east as Winnipeg and west to Edmonton" of Sunday evening's fireball. Accounts include a sonic boom, ground tremors, and a sulfur odor. It notes that only 14 meteorites have been found in Saskatchewan since 1913. Residents are asked to look around now while the object is fresh, and the ground is hard and covered with snow.

The Calgary, Alberta Herald in "Fireball streaks across Prairies" tells today that "the University of Calgary's automatic sky search camera . . . fish-eye lens caught the streak of light and two bright flashes at 7:33 p.m." (See movie and details here.) The article reports that the Canadian military says this was not re-entering space debris. The Winnipeg, Manitoba Sun also has a report today, and says that "To date, there have only been seven meteorites ever found in Manitoba." See more links from A/CC yesterday ("Manitoba event").

Risk monitoring 23 March

The Tuesday Daily Orbit Update MPEC carries observation of 2004 FU4 from LINEAR in New Mexico from Friday and yesterday, adding nearly a full day to the beginning of what had been a two-day observing arc and about seven minutes to the end.

Today NEODyS joined JPL in posting this object. JPL increased its impact solution count from six to 15 (with now the first just over six years away), raised its overall ratings, and added about a hundred meters to the rough diameter estimate. There is quite a difference in the JPL and NEODyS assessments, but this is not unusual early in a new object's observing arc, and shows the healthy cross-checking that comes from having two independent risk monitoring activities.

Today's "Risk monitoring" report narrates routine activity in the night-and-day cycle of observation and analysis that identifies and usually soon removes risk possibilities. There is nothing unusual or alarming here. An "impact solution" (aka "virtual impactor" or "VI") is not a prediction but rather a possibility that hasn't been eliminated yet. To learn more, see "Understanding Risk Pages" by Jon Giorgini of JPL, and other links related to this subject.