Category: Asteroids

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Remember a competition we reported on back in April called “Move An Asteroid”? It was an international technical paper competition looking for unique and innovative concepts for how to deflect an asteroid or comet that might be on a collision course for Earth. The winners have been announced and first prize went to Australian PhD student Mary D’Souza who came up with quite a novel concept: wrap the asteroid with reflective sheeting. Such a coating may increase the asteroid’s reflectivity, enabling deflection by solar radiation pressure.

The asteroid in question, known as Apophis, will pass close to Earth in 2029. Although the 207 meter- wide Apophis is not expected to impact Earth, its current trajectory has it approaching Earth no closer than 29,470 km (18,300 miles), which is well inside the orbit of the moon. This, in conjuction with the 100th anniversary of the Tunguska explosion, was the impetus behind the competition.

D’Souza’s paper was titled “A Body Solar Sail Concept for the Deflection of 99942 Apophis.” Her concept involves using a satellite orbiting Apophis to wrap it with ribbons of reflective Mylar sheeting. Covering just half of the asteroid would change its surface from dull to reflective, possibly enough to allow solar pressure to change the asteroid’s trajectory.

“What happens then is light from the sun shines on the body [of the asteroid] so more of it is reflected … and it actually acts to move it away from the sun and the earth,” said D’Souza, a student at University of Queensland’s School of Engineering.

The competition was sponsored by the Space Generation Advisory Council, a group representing youth perspectives on space exploration to the United Nations and national space programs. SGAC said they received submissions to the competition from all over the world. “It is great to see such an interest in this topic from young people all over the world. Hopefully with competitions like this, SGAC can further increase the involvement of youth in this important field of current space research,” said Alex Karl, Co-Chairperson of the SGAC.

By winning the competition, D’Souza will travel to Glasgow at the end of September to present her plan at the International Astronautical Congress.

Second place was awarded to Andrew Bacon of the Department of Electronic and Electrical Engineering at the University of Bath for his paper entitled “The Use of Electromechanical Resonators for the Mitigation of Earth Threatening Asteroids and Comets.” Bacon’s concept involves the use of electromechanical resonators to build up waves within an asteroid or comet that would break it up. He will also present his plan at the IAC.

Sources: Space Generation press release, The Register

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Since waking up in early July from a brief hibernation, the Rosetta space probe has passed yet another milestone on the long journey to its rendezvous with the comet 67/P Churyumov-Gerasimenko in 2014: it has begun tracking the asteroid (2867) Steins. The spacecraft will perform a close flyby of the asteroid on September 5th, 2008, and will spend the next month taking images and science data.

Steins will remain a dot in the sky to the probe for quite a while, but these preliminary images will allow the spacecraft to get a better handle on the orbit of the asteroid, as well as its rotational period. Using the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) camera, it will image the asteroid twice a week until the 25th of August, and then will take daily images until the planned flyby on September 5th. Rosetta will pass within 800 km (500 miles) of the asteroid, imaging and taking data at the relatively slow speed of 8.6 km/second (5.3 miles/second).

The trajectory of Steins has already been established from ground-based observations, but the imaging leading up to the flyby will help to optimize the trajectory of the spacecraft. The location of the asteroid is known to within 100 km presently, but the work Rosetta will be doing will narrow that down to 2 km.

“As Rosetta’s distance from Steins decreases, the precision of the measurements for Steins’ orbit will increase even further, allowing us the best possible trajectory corrections later on before closest approach, especially in early September,” said Sylvain Lodiot, from the Rosetta Flight Control Team at the European Space Operations Centre.

During the flyby of Steins, Rosetta will study the physical and chemical properties of the asteroid. It will also provide scientists with a detailed look into the kinematic properties (how fast it is spinning), and how the asteroid interacts with the solar wind. Being so close to Stein will give Rosetta a chance to analyze any satellites of the asteroid, as well as the gas and dust in the near vicinity.

Rosetta launched in March 2004, and is taking a roundabout way to get to the final destination of comet 67/P Churyumov-Gerasimenko. It has passed by the Earth twice – once in March 2005, and once again in February 2007 – with another flyby scheduled for November 2009. While doing the most recent flyby it took this spectacular image of the Earth at night with the OSIRIS camera. The lighted regions are populated areas on continents in the Northern Hemisphere.

Earth isn’t the only celestial body that the spacecraft has visited, though. It passed within 1,000 km (620 miles) of Mars in Februrary 2007, and will perform a flyby of the asteroid 21 Lutetia in 2010. This game of planetary billiards is meant to adjust the trajectory of the spacecraft, and the imaging done on the Earth, Mars and the asteroids helps the science team work out all of the bugs in the host of science instruments on board.

Once it has arrived at 67/P Churyumov-Gerasimenko, it will deploy a lander, named Philae, which will drill into the comet to study for the first time ever the compositional nature of a comet. Rosetta will orbit the comet, following it around the Sun.

If you want to keep tabs on the progress of the Rosetta mission, the ESA has a flash animation tool that allows you to zoom in on any part of the mission.

Source: ESA Press Release

A rare event has given astronomers a great view of a binary asteroid system. Tonight, asteroid 2008 BT18 passed 1.4 million miles from Earth, shining like a 13th magnitude star. Before July 7th, astronomers believed 2008 BT18 was “just another” near-Earth asteroid, but then the Arecibo radio telescope obtained a “delay-Doppler” image of the asteroid and found it in fact had a binary partner. Although binaries are fairly common in the Solar System, this was a rare opportunity for a ground-based telescope to capture such a clear view…

Only last week, Nancy wrote about binary asteroids and double craters found on Earth may be evidence that our planet has been hit by binaries in the past. As the article was being written, the Arecibo radio telescope in Puerto Rico was taking a detailed look at a binary asteroid approaching Earth. Although asteroid 2008 BT18 posed no threat to Earth, astronomers are very keen to learn more about binary asteroids to understand how they form and how they may be deflected from a collision course with Earth should a binary get too close.

About 16% of asteroids in the Solar System are thought to be binaries, so this event was a great opportunity for Arecibo to image 2008 BT18 and it could be seen by amateur astronomers as a 13th magnitude star. The Arecibo observatory has discovered 53% of all near-Earth binaries, so this seasoned radio telescope is an important component in the observation of these objects.

The asteroid binary was fairly sizeable but passed about six times the Earth-Moon distance from us. “The sizes of the two components are 600m for the primary and >200m for the secondary,” said Lance Benner, a scientist from NASA’s Jet Propulsion Laboratory (JPL). “The primary looks spheroidal, but we don’t yet know about the shape of the secondary.”

Other telescopes are analyzing the binary orbit, asteroid masses and density of the two objects, such as NASA’s Goldstone radar in the Mojave Desert, California. Although Goldstone is smaller than Arecibo, there is a strong echo for scientists to analyze the data collected from the passage of the asteroid pair. According to spaceweather.com, observers in the Southern Hemisphere had the opportunity to see 2008 BT18 pass through the constellation of Canis Major, heading south.

Source: Spaceweather.com

Asteroids with moons, called binary asteroids, are fairly common in the solar system. But scientists haven’t been able to figure out the dynamics of these asteroids, especially how the moons form. But a group of astronomers studying binary asteroids say the surprising answer is sunlight, which can increase or decrease the spin rate of an asteroid. The researchers also say that since there are a number of “double craters” on Earth – side-by side craters that appear to have formed at about the same time — these binary asteroids may have hit our planet in the past. The image above is of twin circular lakes in Quebec, Canada, formed by the impact of an asteroidal pair which slammed into the planet approximately 290 million years ago. Similar double craters also can be found on other planets, as well.

Derek Richardson, of the University of Maryland, and Kevin Walsh and Patrick Michel at the Cote d’Azur Observatory, France outline a model showing that when solar energy “spins up” a “rubble pile” asteroid to a sufficiently fast rate, material is slung off from around the asteroid’s equator. This process also exposes fresh material at the poles of the asteroid.

If the spun off bits of asteroid rubble shed sufficient excess motion through collisions with each other, then the material coalesces into a satellite that continues to orbit its parent.

Link to an animated model of the spin-up and binary formation from two views, on the left is an overhead view. The right pane of the movie looks at the equator of the primary body, which is also the plane in which the asteroid’s satellite is formed (courtesy of the authors of the study).

Because the team’s model closely matches observations from binary asteroids, it neatly fills in missing pieces to a solar system puzzle. And, it could have much more down-to-earth implications as well. The model gives information on the shapes and structure of near-Earth binary asteroids that could be vital should such a pair need to be deflected away from a collision course with Earth.
The authors say that their current findings also suggest that a space mission to a binary asteroid could bring back material that might shed new light on the solar system’s early history. The oldest material in an asteroid should lie underneath its surface, explained Richardson, and the process of spinning off this surface material from the primary asteroid body to form its moon, or secondary body, should uncover the deeper older material.

“Thus a mission to collect and return a sample from the primary body of such a binary asteroid could give us information about the older, more pristine material inside an asteroid,” Richardson said.

Original News Source: PhysOrg

About 13,000 years ago, woolly mammoths roamed the North American continent and the first known human society in that region, known as the Clovis civilization, lived there as well. But geologic and archeological evidence shows they both suddenly disappeared, and scientists have long debated the mystery of the mass extinction of both animals and humans about 12,900 years ago. At that time, climatic history suggests the Ice Age should have been drawing to a close, but instead rapid climate change initiated an additional 1,300 years of glacial conditions. But scientists couldn’t agree on the cause of the sudden change in climate. However, about two years ago geophysicist Allen West proposed that an asteroid or comet exploded just above the earth’s surface at that time over modern-day Canada, sparking a massive shock wave and heat-generating event that set large parts of the northern hemisphere ablaze, setting the stage for the extinctions. Another scientist set out to prove West wrong, but ended up finding evidence to support the exploding asteroid/comet theory.

Ken Tankersley, Anthropology professor at the University of Cincinnati studied sites in Ohio and Indiana that offers the strongest support yet for the exploding comet/asteroid theory. Samples of diamonds, gold and silver found in the region have been conclusively sourced through X-ray diffractometry to have come from the diamond fields region of Canada.

Tankersley and West both believe the best scenario to explain the presence of these materials this far south is the kind of cataclysmic explosive event described by West’s theory. “We believe this is the strongest evidence yet indicating a comet impact in that time period,” says Tankersley.

Previously, geologists believed the deposits of the gems and precious metals were brought south from the Great Lakes region by glaciers. But they are found at a soil depth consistent with the time frame of the comet/asteroid event.

“My smoking gun to disprove (West) was going to be the gold, silver and diamonds,” Tankersley says. “But what I didn’t know at that point was a conclusion he had reached that he had not yet made public – that the likely point of impact for the comet wasn’t just anywhere over Canada, but located over Canada’s diamond-bearing fields. Instead of becoming the basis for rejecting his hypothesis, these items became the very best evidence to support it.”

Additional work is being done at the sites looking for iridium, micro-meteorites and nano-diamonds that bear the markers of the diamond-field region, which also should have been blasted by the impact into this region.

As Tankersley, West and additional scientists compile more data, they’ll be looking for more clues to help explain the history of our planet and its climate.

“The kind of evidence we are finding does suggest that climate change at the end of the last Ice Age was the result of a catastrophic event,” Tankersley says. “The ultimate importance of this kind of work is showing that we can’t control everything,” he says. “Our planet has been hit by asteroids many times throughout its history, and when that happens, it does produce climate change.”

Original Source: Science Daily