NASA has come up with its best estimate of the number of potentially hazardous asteroids in our solar system.
PHAs, as they’re known, are asteroids large enough to survive entry into Earth’s atmosphere. Impacts could cause regional damage or global catastrophes. All of the asteroids pass within 5 million miles of our planet.
How many are there?
More than a few.
The estimate was made based on observations by NASA’s Wide-field Infrared Survey Explorer (WISE). The asteroid-hunting portion of the explorer’s duties are called NEOWISE.
“The project samples 107 PHAs to make predictions about the entire population as a whole,” NASA posted today on its website. “Findings indicate there are roughly 4,700 PHAs, plus or minus 1,500, with diameters larger than 330 feet (about 100 meters). So far, an estimated 20 to 30 percent of these objects have been found.”
The website quotes Lindley Johnson, program executive for NASA’s Near-Earth Object Observation Program.
“The NEOWISE analysis shows us we’ve made a good start at finding those objects that truly represent an impact hazard to Earth,” he said. “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.”
Twice as many asteroids as previously thought are in lower-inclination orbits, which could align closely with the Earth’s orbit. That could open the door for interception missions, landing people or robots on their surface.
For more, check out the NASA website.