By Peter Becker
The meteor that exploded over Russia in February, resulting in widespread damage and injuries when the sonic boom struck, awakened us again that our planet is in the line of fire.
This should be of no surprise. Just look at the Moon through any size telescope or even binoculars held steady. It's loaded with craters; craters upon craters, jumbled and uplifted rides, valleys, rifts and dark plains where lava long ago covered parts of the rough landscape.
Full Moon is on May 25th; craters are not as easily picked out at this stage because sunlight is beaming straight down and reflected straight back to admiring eyes on Earth. The easiest time to look for lunar craters is on any clear night centered a few nights around first or last quarter.
Literally thousands of craters of many sizes may be seen with a small telescope, a view that does not fail to astonish ever since Galileo first looked at them through a crude telescope over 400 years ago.
On Earth, thankfully most meteors are small enough to vaporize in the upper atmosphere before striking the ground. A few large ones have made it down, and we even have examples of craters. Most craters left on Earth by large meteors or asteroids have been eroded away through ages of inclement weather.
On the Moon there is no weather, inclement or otherwise (clement?).
Thus, the craters stay for the eons, eroded only by pounding of subsequent bombardments and zapping by cosmic rays.
So with all the meteor showers that pepper the Moon as well as the Earth, how come we don't see new craters with our telescope now and then?
The answer is that most strikes are by space rocks too small to make an impact easily visible from earthbound telescopes. That's really good because a big impact on the near side of the Moon would likely send moon rocks our way.
On St. Patrick's Day, March 17, a bright flash was seen on the darkened portion of the thick crescent Moon. NASA's Meteoroid Environment Office monitors video of the Moon's night side, and about every week detects a very brief and tiny flash caused by a meteor strike. This time the flash was so bright it could have been seen by unaided eyes if you were looking at the right moment.
The monitoring is done to assess the hazards to future lunar explorers.
The same night, five bright fireballs were recorded in the Earth's atmosphere. William Cooke of NASA, who leads the project, suspects the events were related and that the rock that hit the Moon was about the size of a beach ball.
NASA's Lunar Reconnaissance Orbiter is searching for a new crater, suspected to be 20 feet wide.
Send your notes to firstname.lastname@example.org. For a video and more information on the March 17th lunar meteor, visit www.skyandtelescope.com.
Keep looking up!