May 17, 2012
NASA Keeping An Eye Out For Dangerous Asteroids
NASA has just received observations from its WISE (or Wide-field Infrared Survey Explorer) mission, giving them the best assessment thus far of how many PHAs (potentially hazardous asteroids) are floating around in our solar system. Now, the team at NASA can count these PHAs, discover their origins and predict what kind of harm they may pose to Earth.
According to a report from NASA´s Jet Propulsion Laboratory in Pasadena, these PHAs are a subset of a larger group of near-Earth asteroids and have the closest orbits to our planet, often within 5 million miles. The newly studied PHAs may also be large enough to survive a journey through Earth´s atmosphere, making them a potential threat to our planet.These new findings come courtesy of NEOWISE, the asteroid-hunting portion of the WISE mission. To make their predictions, the team at NEOWISE sampled 107 PHAs and found there are roughly 4,700 PHAs measuring 330 feet in diameter. So far, the team says they have found 20 to 30 percent of these PHAs.
So far the NEOWISE team is finding their predictions are largely in line with previous guesses, though they say their measurements will provide a more accurate and complete look at PHA sizes and populations.
"The NEOWISE analysis shows us we've made a good start at finding those objects that truly represent an impact hazard to Earth," said Lindley Johnson, program executive for the Near-Earth Object Observation Program at NASA Headquarters in a press release. "But we've many more to find, and it will take a concerted effort during the next couple of decades to find all of them that could do serious damage or be a mission destination in the future."
The new NEOWISE analysis also suggests there are twice as many PHAs in “lower-inclination” orbits than they once thought. This means the PHAs are better aligned with the plane of Earth´s orbit. Furthermore, the lower-inclination PHAs are smaller and brighter than other near-Earth asteroids previously studied. A larger body may have broken up the main belt between Jupiter and Mars, sending fragments-turned-PHA towards Earth.
With these PHAs on the same plane as Earth, NASA says they may be able to send human or robotic missions out to study these asteroids.
"NASA's NEOWISE project, which wasn't originally planned as part of WISE, has turned out to be a huge bonus," said Amy Mainzer, NEOWISE principal investigator.
“Everything we can learn about these objects helps us understand their origins and fate. Our team was surprised to find the overabundance of low-inclination PHAs. Because they will tend to make more close approaches to Earth, these targets can provide the best opportunities for the next generation of human and robotic exploration."
Since the smaller asteroids are also brighter, scientists at NASA suggest they may be stony, composed of granite, or be metallic in nature. The more the scientists know about these PHAs, the better they are able to predict what kind of harm, if any, could be inflicted on Earth by these asteroids. Depending on what they are made of, the asteroids could burn up entirely or survive the descent through our atmosphere.