Normally in this column, I discuss satellites or spacecrafts that have been or will be launched through the Earth’s atmosphere into orbit. This month the tables have turned as I will discuss the possibility of an asteroid entering the Earth’s atmosphere and colliding with our planet. Queue the Star Wars intro theme, which is actually from 2001: a Space Odyssey…
Discovered in January of 2011 by the Catalina Sky Survey managed through the University of Arizona in Tucson, the potentially hazardous asteroid (PHA) only has a slim chance of impacting Earth in 2040. The rock, named asteroid 2011 AG5, is 460 feet or 140 meters in size and would damage an area around 100-miles wide if it crashed into Earth. Currently, the asteroid is outside of Mars’ orbit and on the other side of the sun, making it too far away to see and thus not ideal conditions for observation. Using the current data and analysis, a workshop was held at NASA’s Goddard Space Flight Center in Greenbelt, Maryland to discuss the observations and the likelihood of an impact. The workshop included engineers and scientists from across the globe and they concluded that asteroid 2011 AG5 has less than a 1% chance of impacting Earth.
Late in 2013, the asteroid will be visible in the late evening sky with much better conditions for viewing. At this point, the asteroid will be 91 million miles from Earth. 2011 AG5 will be observed by the Near-Earth Object Observation Program (NEO) and more will be know about its fate in 2023 when the asteroid has a chance of passing through the keyhole. The keyhole is a 227 mile wide area that is affected by the Earth’s gravitational pull. If the asteroid passes into the keyhole, it could be grabbed by Earth’s gravity and pulled in for an impact. If the asteroid misses the keyhole, Earth dodges a bullet. When this occurs in 2023, the asteroid will be 1.1 million miles away. If the asteroid is captured by the Earth’s gravitational pull, the impact is estimated to occur on February 5, 2040.
PHA’s are not rare occurrences as observations from NASA’s Wide-field Infrared Survey Explorer (WISE) have assisted scientists in estimating their numbers to be around 4,700 in our solar system. PHA’s are a subset of asteroids that will pass within a few million miles of Earth and are large enough to survive the Earth’s atmosphere and make impact with our planet. So far, 20% to 30% of these asteroids have been detected. As we hurl through space, we are often oblivious to our own vulnerability: we are not just one of 9 planets orbiting the Sun; rather we are accompanied on this orbit by countless amounts of space debris and rocks, all spinning through our solar system and often colliding with each other. Earth is lucky to have Jupiter as a shield with a massive gravitational pull; and while we can’t dodge every bullet, hopefully we can avoid the worst of them.