Double trouble? 2 comets to fly close to Earth hours from now: 'One for the record books'

Comet 252P/LINEAR will safely fly past Earth on March 21, 2016, at a range of about 3.3 million miles (5.2 million kilometers). The following day, comet P/2016 BA14 will safely fly by our planet at a distance of about 2.2 million miles (3.5 million kilometers).(NASA/JPL-Caltech)

For the past months, various space objects have been making close approaches to Earth, triggering fears that one of them could hit the planet and cause massive destruction. This week, our planet will have to contend with not just one, but two comets, that will come in close contact with Earth.

The first one—an emerald-green comet—will brush past Earth on Monday, March 21. This comet, the bigger one between the two space objects currently approaching our planet, is expected to create a spectacle in the southern hemisphere, where it will be visible to the naked eye particularly in areas far from city lights.

In the United States, the huge comet, which is formally called "comet 252P/LINEAR," will also be visible, but only through the use of binoculars. It will glow bright green because of the carbon gas it is puffing out.

More powerful telescopes, such as the Hubble Space Telescope and the powerful ground-based Gemini, will also be observing the twin comets to get a glimpse of these space objects usually only seen from a distance.

Scientists are also excited with the second comet, which will swerve close to Earth on Tuesday. In fact, this one will be the closest comet to ever come near our planet in a span of 250 years.

This comet, formally called P/2016 BA14, was only discovered a few months ago. If taken together with 252P, they will be "among the closest comets to pass by Earth in recorded history," according to University of Maryland's Matthew Knight.

Michael Kelley of the University of Maryland, meanwhile, described the double comet fly-by as "one for the record books."

"It's a fantastic opportunity for professionals to learn more about comets, and if you have a chance to try to find them ... it's a fantastic chance to see part of history as it happens," Kelley told USA Today.

Space scientists are still determining the relationship between the two comets, but they think BA14 is likely from 252P.

"Comets split relatively often, but we rarely get a chance to study them soon after it happens, and when we do usually only the bigger fragment survives. ...We have two fragments in this case," Knight explained.