Comets Could Be More Dangerous Than Previously Thought

When thinking about extinction-level impact caused by an object from outer space, people often think about a killer asteroid. However, scientists at NASA urge people to have a broader mind and consider the real danger of an incoming comet.

According to a report from The Guardian, the Earth had two close encounters with potential killer comets. The first one occurred in 1996 when an aberrant comet flew into Jupiter. The second encounter occurred in 2014 when a comet passed "within cosmic spitting distance of Mars."

"Comets have largely been ignored by people that are interested in defending the planet," Joseph Nuth, a researcher at NASA's Goddard Space Flight Center in Greenbelt, Maryland, in a report from Space.com.

Nuth noted that the lack of attention in comets was possibly caused by the perception that nothing can be done about it, which is totally true at present time. Comets, unlike near-Earth asteroids, spends majority of their time in the dark "corners" of the space. Due to this, comets are much more difficult to spot than asteroids.

As an example, the comet that occurred in 2014 was first discovered in January 2013. The 0.3-mile-wide Comet Siding Spring came within 87,000 miles of the red planet just 22 months after being detected. On average, producing and launching a highly-reliable spacecraft to deflect the comet will take up to five years.

Aside from the element of surprise, the size and high velocity of comets made it more concerning than asteroids. Their highly conducive orbit could make comets more conducive to direct hits.

Despite being relatively rare, comet strikes still pose great danger on Earth. Due to this, scientists were trying to increase the Earth's defenses against possible asteroid and comet impacts. NASA has recently established a planetary defense office.

There are two possible ways to prevent extinction-level asteroid or comet strikes. The first method is basically just hitting the incoming asteroid or comet with nuclear warhead, making it explode. The second method is hitting the asteroid or comet with a kinetic impactor, which is basically a giant cannonball.