Sixty some million years ago, the Earth had a really bad day. A big piece of space rock slammed into the planet and took out Barney, Yoshi, and the whole Land Before Time crew. These catastrophic, species-ending events happen on occasion. For most of human history, we've remained blissfully ignorant of the times when civilization just baaaaarrely missed being erased. But that ignorance has (thankfully?) been lifted.

Scientists now have the tools to track these sky borne threats, including all the misses that came uncomfortably close. Recently, the comets P/2016 BA14 and 252P/LINEAR swooped in from the far reaches of the solar system for some (comparatively) close encounters. While there's a multi-million-mile buffer in between us and oblivion, these flybys will prove to be ones for the record books.

To reiterate, neither the Earth nor any of its inhabitants are in any imminent danger of the sky falling on them. NASA tracks these potentially cataclysmic Near Earth Objects (or "NEOs") and has confirmed that there is zero chance of impact. However, they will come in tantalizingly close. Relatively speaking.

Just to illustrate how little impact (excuse the pun) these flybys will have on most people's lives, the 750-foot wide 252P already had its closest approach at 8:14 a.m. ET this morning. (Did you notice?) The dirty snowball came in around 3.3 million miles from the Earth. While that is a sizeable space cushion (about 14 times further than the moon, in fact), this approach still manages to be the fifth closest ever recorded.

Meanwhile, at around 7:30 a.m. tomorrow P/2016 (whose exact size remains unclear) will swoop in as close as 2.2 million miles, making it the third closest comet flyby in history.

While the world will almost certainly still be around come Wednesday (as far as the cosmos is concerned), we should pause to consider how recently these events came under our figurative (and literal) radar. While 252P/LINEAR was discovered nearly 16 years ago by MIT's Lincoln Near Earth Asteroid Research (LINEAR) program, the far-closer approaching P/2016 was only discovered in January of this year.

These recent events mirror an incident on Halloween last year when a stadium-sized asteroid came in as close of the moon, but was—frighteningly—only discovered a few weeks before its closest approach. While that hunk of rock was still far smaller than the one that took out the dinosaurs (thought to be around five miles wide), it was probably larger than the Tunguska event impact in 1908 which released 1,000 times more energy than the atomic bomb dropped on Hiroshima.

Sleep well, everybody!

Since the two comets follow such similar orbits, scientists believe they were "twins" born of the same parent comet. "Comet P/2016 BA14 is possibly a fragment of 252P/LINEAR. The two could be related because their orbits are so remarkably similar," said Paul Chodas, manager of NASA's Center of NEO Studies (CNEOS) in a blog post. "We know comets are relatively fragile things, as in 1993 when comet Shoemaker-Levy 9 was discovered and its pieces linked to a flyby of Jupiter. Perhaps during a previous pass through the inner-solar system, or during a distant flyby of Jupiter, a chunk that we now know of as BA14 might have broken off of 252P."

In addition to existential pondering they may inspire, these flybys open the door to observation. The comets are now large enough that anyone (away from a large city) can observe them with a pair of binoculars. Skyandtelescope.com has a handy guide for any sky watchers.