Astro Bob blog: More meteorites, a monster ash plume and an orbiting duetMore news on the Wisconsin fireball, the Iceland volcano, the space shuttle and Mars.
By: Bob King, Duluth News Tribune
More meteorites, a monster ash plume and an orbiting duet
Mike Farmer of Arizona points to his first meteorite find from the Wisconsin
fireball. Most small meteorite fragments are decelerated so much by the
atmosphere they land right on the ground without making holes or craters. Photo
courtesy Michael Johnson
A look inside one of the meteorites from the Wisconsin fall. It shows a mix of white inclusions in a dark matrix, what meteorite researchers describe as a brecciated texture. Dark fusion crust from melting during atmospheric entry is seen at bottom. More information HERE. Credit: John Valley, UW-Madison
As meteorite hunters descend into southern Wisconsin like so many bees drawn to nectar, we'll soon have news if more than a couple of meteorites will be found from this week's fireball. The latest I'm aware of was made by Michael Farmer (above) who discovered a 131 gram space rock in a farm field.
During a meteorite fall, much of the original rock, called a meteoroid, vaporizes in the atmosphere due to frictional heating as it plunges earthward between seven and 45 miles per second. Think of the weight loss as a cosmic version of The Biggest Loser. Stresses brought on by air pressures at those speeds can break the remaining object(s) into small pieces which then fall to the ground across an oval-shaped stretch of land called a strewn field. The smallest pieces drop first and are found at one end of the oval while the big ones drop last and are at the other end. To give you an idea of what a strewnfield looks like, I've included a map made by Svend Buhl of the Pultusk meteorite fall in Poland in 1868.
The size and exact shape of the oval depend upon many factors: the object's speed, angle of entry, how fragile the material is and the local wind speeds at the time of the fall. Wonderful to think we just received a visitor from the asteroid belt that's been out in space since the dawn of the solar system minding it's own business for four and half billion years. Scientists are eager to examine the meteorite to determine its composition, whether it broke off from a larger object and if so, how long it's been out there since.
The ash plume from Iceland's volcano stretches well into the North Atlantic Ocean in this photo made by NASA's Terra satellite on April 15. Credit: NASA image by Jeff Schmaltz, MODIS Rapid Response Team
Seems like the Earth's been busy lately with volcanoes, earthquakes and now the recent meteorite fall. Must be the end of the world, right? Hardly. It just goes to show what a lively place our ancient planet still is. Like my young daughters, Earth's full of surprises.
Iceland's Eyjafjallajokull volcano has sent a large cloud of ash Europe's way not only stopping much of that region's air traffic but also creating vivid sunrises and sunsets. By the way, the volcano's name is pronounced something like this: AY-yuh-fyat-LIE-uh-goot. The first syllable "AY" sounds like the "a" in "made". For a page of absolutely spectacular images of the volcano, I can do no better than direct you to HERE.
The combined shuttle and ISS crews give each other farewell hugs earlier today before the shuttle undocked from the station today. Credit: NASA TV
The space shuttle Discovery undocked earlier this morning from the International Space Station (ISS) and will land Monday. That means we'll have the chance to see the two of them separately but near one another during tomorrow morning's pass. According to information from the Heavens Above site, the ISS will appear first and be followed just seconds later by the shuttle. You can easily tell them apart because the space station is considerably brighter. The two will arc across the northern sky Sunday morning starting at 5:33 a.m. Central time.
Mars is at upper left and under it is the Beehive Cluster. Pollux and Castor, Gemini's brightest stars, are at top right. Details: 35mm lens at f/2.8, ISO 1600 and 25-second time exposure. Photo: Bob King
Last night was clear and fine with the moon and Venus stealing the show. I didn't want to forget Mars though, up there in Cancer the Crab and right above the Beehive star cluster. The contrast between the bright, pinpoint planet and the fuzzy glow of the cluster was really cool. You can easily see them with your naked eye from suburban and rural locations. Binoculars will bring the cluster into view for city dwellers. Here's a previous blog link to help direct you to Mars where you can begin your journey. The planet will remain near the cluster for another few nights.