NASA’s best shot at protecting the Earth from cosmic destruction is spotting giant asteroids well before impact. The US space agency presented the dire conclusion at the 2019 April meeting of the American Physical Society on April 16. Amy Mainzer, a NASA astronomer at the Jet Propulsion Laboratory in California, told the conference catching an asteroid early in its Earth-bound trajectory is the key to safety. Astronomers were acutely made aware of this in 2013 when an undetected asteroid exploded over Russia’s Chelyabinsk Oblast.
The unsuspected asteroid attack damaged more than 7,000 buildings in a wide radius.
And when the 65.6ft-wide (20m) space rock exploded with 30 times the force of the Hiroshima nuclear bomb, shards of glass from broken windows injured more than 1,000 people.
Spotting the asteroid before it entered the Earth’s atmosphere could have helped mitigate the amount of damage.
Dr Mainzer said: “If we find an object only a few days from impact, it greatly limits our choices, so in our search efforts we’ve focused on finding NEOs when they are further away from Earth, providing the maximum amount of time and opening up a wider range of mitigation possibilities.”
NEOs or “Near-Earth Objects” are all comets (NECs) and asteroids (NEAs), which cut dangerously close into the Earth’s orbit of the Sun.
Most of these rocky objects originate in the asteroid belt between Mars and Jupiter but have been nudged deeper into the solar system.
Spotting NEOs before they reach Earth is a vital but incredibly hard task – asteroids are virtually impossible to spot against the dark backdrop of space.
Dr Mainzer likened the job to plucking out pitch-black print toner from the night sky.
She said: “NEOs are intrinsically faint because they are mostly really small and far away from us in space.
If we find an object only a few days from impact, it greatly limits our choices
Amy Mainzer, NASA JPL
“Add to this the fact that some of them are as dark as printer toner and trying to spot them against the black of space is very hard.”
All rocks which orbit the Sun from a distance of 1.3 astronomical units (au) are ranked as NEOs.
One au is the distance from Earth to the Sun of approximately 93 million miles (149.6 million km).
This might seem like a lot to us on Earth but on the grand scale of the cosmos, the distance is insignificant.
Dr Mainzer and her team are now testing new ways in which NASA and other space agency can more effectively monitor space for threats.
Asteroids and comets basking in the Sun’s warmth emit infrared radiation, which can then be picked up by NASA’s state-of-the-art Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) telescope.
The NASA astronomer said: “With the NEOWISE mission we can spot objects regardless of their surface colour, and use it to measure their sizes and other surface properties.”
However, one detected, NASA’s Earth defence options remain daily limited.
One proposed idea is to derail asteroids by hitting or nudging them with special spacecraft – a small orbital correction early on can push an asteroid hundreds of thousands of miles off course in the long run.
Dr Mainz said: “These objects are intrinsically interesting because some are thought to be as old as the original material that made up the solar system.
“One of the things that we have been finding is that NEOs are pretty diverse in composition.”
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