Could An Asteroid Hit Planet Earth, Again?

Could An Asteroid Hit Planet Earth, Again?
ScienceDaily (Jan. 30, 2008) — Earth dodged a bullet today, when asteroid TU24 passed within 540,000 kilometers of our planet, which is just down the street on a galactic scale. Tomorrow, another asteroid – 2007 WD5 – will zip past Mars at a distance of only 26,000 kilometers away. Will we dodge the bullet the next time a near-Earth object (NEO) hurtles dangerously close to our home planet?
To mark the 100th anniversary of the Tunguska event, when an exploding asteroid leveled 2000 square kilometers of Siberian forest, The Planetary Society today kicked off a year-long focus on Target Earth. The asteroid believed responsible for the cataclysm on June 30, 1908 became a fireball from the sky and knocked pine trees over like matchsticks near the Podkamennaya Tunguska River in Russia. Such an explosion today over more populated areas could lay waste an entire city.
“The solar system is a busy place,” said Louis Friedman, Executive Director of The Planetary Society. “In fact, we live in a dangerous neighborhood, and keeping track of NEOs is like organizing a Neighborhood Watch in our corner of space.”
Earth has been hit by NEOs many times in the past; ancient craters are still visible in landforms around the world. The famed Meteor Crater in Arizona and Canada’s Lake Manicouagan are only two examples.
Target Earth will focus on a variety of NEO projects supported by The Planetary Society, including the Apophis Mission Design Competition, the Gene Shoemaker Near Earth Object Grants, NEO mission advocacy, and a one-hour HD TV “Daily Planet” special on asteroids being produced by Discovery Canada.
In mid-to late February, the Society will announce the winners of the Apophis Mission Design Competition, which invited participants to compete for $50,000 in prizes by designing a mission to rendezvous with and "tag" a potentially dangerous near-Earth asteroid. The competition received 37 mission proposals from 19 countries on 6 continents.
Tagging may be necessary to track an asteroid accurately enough to determine whether it will impact Earth, thus helping space agencies to decide whether to mount a deflection mission to alter its orbit. Apophis is an approximately 400-meter NEO, which will come closer to Earth in 2029 than the orbit of our geostationary satellites – close enough to be visible to the naked eye. If Apophis passes through a several hundred-meter wide "keyhole" in 2029, it will impact Earth in 2036. While current estimates rate the probability of impact as very low, Apophis is being used as an example to enable design of a broader type of mission to any potentially dangerous asteroid.
"Target Earth encompasses The Planetary Society’s three-pronged approach to NEO research,” said Director of Projects Bruce Betts. "We fund researchers who discover and track asteroids, advocate greater NEO research funding by the government, and help spur the development of possible ways to avert disaster should a potentially dangerous asteroid be discovered."
The Society will call for another round of Shoemaker grant proposals in the summer of 2008. One past grant recipient, Roy Tucker from Arizona, co-discovered Apophis. Many other past recipients from around the world continue to discover, track, and characterize NEOs.
NASA currently has no plans to study methods of asteroid deflection, or how to tag an asteroid for precise tracking. NASA and the European Space Agency (ESA) have co-sponsored the Society’s Apophis competition and will study the best mission designs offered.
The $50,000 in prize money for the Apophis Mission Design competition was contributed by The Planetary Society's Chairman of the Board, Dan Geraci, together with donations from Planetary Society members around the world. Funding for the Gene Shoemaker NEO Grant program comes from Planetary Society members.
Adapted from materials provided by Planetary Society.