Courtesy NASA/JPL-Caltech/UMDThe following is from a listserv I am on that I thought was interesting.
On February 14, NASA's Stardust-NExT (New Exploration of Tempel 1) mission will encounter Comet Tempel 1, providing a unique opportunity to measure the dust properties of two separate comets (Wild 2 and Tempel 1) with the same instrument for accurate data comparison. The encounter will also provide a comparison between two observations of a single comet, Tempel 1, taken before and after a single orbital pass around the sun.
NASA's Stardust spacecraft will fly within 200 kilometers (about 124 miles) of Comet Tempel 1 on February 14, 2011, at about 8:36 p.m. Pacific Standard Time.
NASA's Deep Impact mission observed Comet Tempel 1 in the summer of 2005, as the comet was inbound toward the Sun on its approximately 5.5-year orbit between Mars and Jupiter. Deep Impact's primary mission was to deliver a special impactor spacecraft into the path of Comet Tempel 1. The spacecraft -- and many ground-based observers -- observed the impact and the ejected material. Scientists were surprised the cloud was composed of a fine, powdery material, not the expected water, ice, and dirt. The spacecraft did find the first evidence of surface ice on the surface of a comet instead of just inside a comet.
The Stardust-NExT mission is a low-cost use of an in-flight spacecraft redirected to a new target. Prior to its tasking for Tempel 1, the Stardust spacecraft successfully flew through the cloud of dust that surrounds the nucleus of comet Wild 2 in Jan. 2004. The particles of cometary material and gathered during this flyby were then returned to Earth aboard a sample return capsule which landed in the Utah desert in January 2006.
Courtesy NASA, ESA, and H. Weaver (The Johns Hopkins University/Applied Physics Lab) Periodic comet 103P/Hartley 2is currently visible high in the evening sky. Learn more here.
A new theory suggests that a blast from space 13,000 years ago may have been responsible for changes in Ice Age human cultures, and for wiping out most of North America’s large mammals, a fate similar to what large dinosaurs may have met 65 million years earlier.
The extraterrestrial blast from a large object, such as a comet or asteroid, colliding with Earth would have caused a significant climate cooling over the North American continent lasting for centuries.
According to Dr. Richard Firestone of Lawrence Berkeley National Laboratory, in California, the source of the collision may have originated from a supernova explosion that occurred about 250 light years from Earth.
“Our research indicates that a 10-kilometer-wide comet, which may have been composed from the remnants of a supernova explosion, could have hit North America 13,000 years ago,” says Firestone. “This event was preceded by an intense blast of iron-rich grains that impacted the planet roughly 34,000 years ago.”
Firestone and co-researcher Alan West say evidence of the supernova’s initial shockwave can be found in tiny impact craters in 34,000 year-old mammoths tusks. The two men theorize the tiny craters are the results of iron-rich grains traveling at 10,000 kilometers per hour slamming into the enamel.
Other evidence supports the comet impact theory. Sediment layers at some 22 prehistoric sites across the continent, show high of levels of iridium, along with concentrations of tiny diamond chips called nanodiamonds. There’s also a black layer of high carbon content that researchers argue could be the remains from wildfires ignited by the blast that swept across the continent.
No crater is known but scientists suggest that ice sheets present at the time may have been thick enough to act as a buffer against the collision.
It’s also possible the space rock exploded in the atmosphere but even then a shockwave of intense heat that would have wiped out everything in its path for miles around, and would have caused immediate and long-term damage to any existing human cultures. Glacial ice would have melted and surged into the North Atlantic, changing currents and effects on climate for centuries.
Such an event seems to coincide with the onset of what’s known as the Younger Dryas Episode, a period of significant environmental changes, Paleolithic cultural development, and mega-fauna extinctions.
All the large mammals that once populated the North and South Americas disappeared suddenly right about the estimated time of the extra-terrestrial impact.
"All the elephants, including the mastodon and the mammoth, all the ground sloths, including the giant ground sloth - which, when standing on its hind legs, would have been as big as a mammoth," said Professor James Kennett, from the University of California in Santa Barbara.
"All the horses went out, all the North American camels went out. There were large carnivores like the sabre-toothed cat and an enormous bear called the short-faced bear."
The effects of such a sudden extinction would certainly impact human populations as well. And that seems to be what happened. A number of prehistoric cultures such as the Clovis seem to have disappeared around the same time.
The new theory will be presented and hashed out this week at the American Geophysical Union's Joint Meeting in Acapulco, Mexico.
LINKS AND MORE INFO
I love Earth & Sky radio's skywatching center. It always features tonight's sky chart and weather, plus skywatching tips and any news. Find out when the moon will rise, what phase of the moon we're in, and where visible planets will be in the sky and when you should look. Plus, it's packed with links to other resources, like interviews with scientists and web planetariums. And you can blog! Check it out...
An impressive display of meteors will move across the sky on Friday, August 12, (2005) when the Perseid meteor shower becomes most visible. Peak viewing times will be from 2 a.m. until sunrise that morning, according to NASA experts. Because of interference from urban lights, viewing is best outside of the city. The Perseid meteor shower occurs every summer, when the tail behind Comet Swift-Tuttle intersects with Earth's orbit, causing comet dust to enter Earth's atmosphere. Meteors from the comet travel from the direction of the constellation Perseus, which gives the shower its name.