NEO News is a newsletter about near earth asteroids and related topics. The opinions here are those of the author, David Morrison, and do not represent NASA or any other organization. You may quote or use these comments as long as you note the original source.

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ARM Option B Selected (March 25)

NASA has just announced the selection of ARM Option B – the alternative ARM mission to pluck a boulder off a larger NEA and return it to the vicinity of the Moon. The rock could be up to 4m in size. Launch is planned for 2020. The estimated costs are slightly larger than Option A, but since this mission involves studying a larger asteroid target (with a stay there of up to 400 days), it is more applicable to a variety of NASA interests, including testing the gravity tractor for planetary defense. The next steps in this mission are a Phase A study, and specific decisions that need to be made this year on defining the solar electric propulsion system. Three NEAs are currently considered potential targets.

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Fast Spinning Asteroid Coming Apart (CNET, March 24)

[http://www.cnet.com/au/news/weird-asteroid-spun-so-fast-it-literally-exploded-itself/]

For many years, a rare class of so-called “active asteroids” that appear to throw off a trail of dust and debris like a comet have puzzled scientists. In 2010, a new sub-type of active asteroid was discovered that appeared to spontaneously eject a shot of dust for no apparent reason. One of the popular explanations floated for the new phenomenon was that these asteroids were undertaking a radical form of cosmic weight loss called “rotational disruption. Basically, the idea was that these asteroids were spinning so fast that the centrifugal forces were able to exceed that of their own gravity and cause the asteroids to begin to break apart.

Finally, for the first time, a team of astronomers was able to observe an active asteroid suspected of going through rotational disruption and capture it after ejecting fragments of itself into space that continue to trail the asteroid like a comet’s tail.

“When we pointed Keck II (a large telescope on Hawaii’s Mauna Kea) at P/2012 F5 last August, we hoped to measure how fast it rotated and check whether it had sizable fragments. And the data showed us all that,” said Michal Drahus, of the Jagiellonian University in Poland, in a release.

At least four fragments of the object can be seen in its tail in the resulting images. The asteroid was known to have thrown off some debris in 2011, but it was initially too dusty when it was discovered for astronomers to get a good look. It now seems that the asteroid was once a larger object, but broke apart, leaving the existing smaller nucleus and its dusty tail.

The team also determined that P/2012 F5 has a very short rotation time of just 3.24 hours, which they say is “fast enough to cause the object to impulsively explode” and is currently the fastest measured among known active asteroids. “This is really cool because fast rotation has been suspected of catapulting dust and triggering fragmentation of some active asteroids and comets,” Drahus said. “But up until now we couldn’t fully test this hypothesis as we didn’t know how fast fragmented objects rotate.”

Drahus concedes that although the team’s data is consistent with the rotational disruption scenario, alternative explanations for the asteroid’s breakup, like a collision with a smaller object at high speeds, can’t be completely ruled out yet.

The findings were published in Astrophysical Journal Letters.

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UN Completes Planning Phase (Space News, March 6)

By Leonard David

[http://www.space.com/28755-dangerous-asteroids-united-nations-team.html]

A special United Nations team on hazardous asteroids has been dissolved after completing its task of setting up organizations to deal with planet-threatening space rocks. The UN’s Scientific and Technical Subcommittee of the Committee on the Peaceful Uses of Outer Space formally dissolved its Action Team 14, in recognition of the group’s successful completion of its mandate to coordinate international mitigation efforts for near-Earth object (NEO) threats, officials announced last month.

Action Team 14 coordinated the establishment of the Space Mission Planning Advisory Group (SMPAG) and the International Asteroid Warning Network (IAWN), and thus played a vital role in the international community’s response to any potential near-Earth object impact threat,” said Elöd Both of Hungary, chair of the subcommittee. …

IAWN’s purpose is to establish a worldwide effort to detect, track and physically characterize NEOs, to determine those that are potential impact threats to Earth. This network consists of a partnership of scientific institutions, observatories and other interested parties performing observations, orbit computation, modeling, and additional scientific research related to the impact potential and effects of asteroids.

The primary purpose of the SMPAG is to prepare for an international response to an NEO threat through the exchange of information, development of options for collaborative research and mission opportunities, and conducting NEO threat mitigation planning. SMPAG is currently chaired by the European Space Agency (ESA).

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NEO News (now in its twentieth year of distribution) is an informal compilation of news and opinion dealing with Near Earth Objects (NEOs) and their impacts. These opinions are the responsibility of the individual authors and do not represent the positions of NASA, Ames Research Center, the International Astronomical Union, or any other organization. If anyone wishes to copy or redistribute original material from these notes, fully or in part, please include this disclaimer.

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