Phil Plait says "Don't Panic!" and he should know because he is the Death from the Skies!: The Science Behind the End of the World which is about things hitting the earth. The object is called 2014 RC and it was discovered on September 2nd. It will arrive on Sunday.
The object is about 20 meter across, and Phil told me on twitter yesterday that this is roughly the same size as the Chelyabinsk asteroid that made a pass over Russia last year.
Remember. Random events occur in clusters. Otherwise they would be called "regular events." So there is probably no meaning to two similar objects coming near Earth in the same geological instant.
2014 RC will come to nearly within the zone that our higher satellites orbit, a fraction of the distance between the Earth and the Moon. Even though you can see some of those satellites, this object is not shiny so you'll need a pretty good telescope to spot it.
In 2008 a 4.1 meter diameter asteroid named 2008 TC3 entered the atmosphere and exploded 37,000 kilometers above Sudan, creating 600 or so meteorites (that were recovered) weighting a total of 10.5 kilos. That was the first time astronomers spotted an object in outer(ish) space and predicted its impact. In 2014, 2014 AA, between 21 and 4 meters in diameter, was spotted by astronomers and 21 hours later hit the planet's atmosphere. It probably hit the Atlantic Ocean near West Africa. The similar sized Chelyabinsk asteroid, the one that exploded over Russia, caused uncounted injuries (but several, probably over 1000) mainly from people running to their windows to see what the bright light was, and getting hit with glass when their windows blew apart; the bill for repairing damaged property came to about $33,000,000.
So the three comparative examples we have don't help much if you want to know the answer to the question "what if an object this size hits the earth." One went into the sea, one totally exploded leaving many fragments to fall on Sudan, and one blew up at a glancing angle. Chances are, if 2014 RC was aimed directly at the planet in a perpendicular angle, it would either blow to bits or become much smaller on the way down. Meteor Crater, in Arizona, is over one kilometer across and was probably caused by an object about 50 meters across (when it hit). A similar sized object created Tswaing crater, in South Africa. While these and similar impacts would have had very serious effects near the site, such as disintegrating nearby living things, the impacts were not sufficient to have left a record in the paleontology or archaeology of the regions. Or we're not looking hard enough. It is safe to surmise that if a few-meters-wide object made impact with the Earth in a populated area, it would be a major disaster, but if it did so in the ocean it would probably not have large effects.
The interesting thing about 2014 RC is, of course, that it was only just discovered. So much for the idea of building a Destroyinator in time to stop an object this size that happens to be aimed at us from striking its target. That approach, apparently, is for larger objects. But still, as Phil Plait says, the science of keeping track of near Earth objects is underfunded.
...at the very least, we need bigger ‘scopes for asteroid searches. We’re doing pretty well in that department, with Pan-STARRS, and the LSST (which is still some years away from operating). But even then they can’t cover the whole sky, which is why I support the efforts of both the B612 Foundation and NASA’s NEOCam. A lot of science will come from these missions at the very least, and who knows? If they do spot a rock with our name on it, at least we’ll get the chance to do something about.
Do you want to see 2014 RC? No problem. Just follow the instructions from Universe Today:
Seeing it will take careful planning. Unlike a star or planet, this space rock will be faint and barreling across the sky at a high rate of speed. Discovered at magnitude +19, 2014 RC will brighten to magnitude +14 during the early morning hours of September 7th. Even experienced amateurs with beefy telescopes will find it a challenging object in southern Aquarius both because of low altitude and the unwelcome presence of a nearly full moon.
Closest approach happens in daylight for North and South America , but southern hemisphere observers might spot it with a 6-inch scope as a magnitude +11.5 “star” zipping across the constellations Pictor and Puppis. 2014 RC fades rapidly after its swing by Earth and will quickly become impossible to see in all amateur telescopes, though time exposure photography will keep the interloper in view for a few additional hours.
And remember, Amateur astronomers: pics or it didn't happen!
The graphic above is from NASA, where you will find additional information.
Not so much "over Russia" as "INTO Russia", Greg! (It *is* their airspace, and fragments did reach the ground...)
And you forgot Tunguska, if you want to consider "what if" impacts that relate to actual, documented events...
All else being equal, damage will also depend on the meteorite's composition. Carbonaceous chondrites can contain high percentages (up to 22%) water as well as organic material. Some others are just rock piles that break up immediately in the atmosphere, while others are solid nickel-iron which means greater mass per volume so more energy potential.
Well, early detection is the thing. However, If one gets lucky and the asteroid is of 'rubble pile' nature AND rotating then it may be possible to just 'blow it up' and let the centripital acceleration scatter it to the 4, um, ... , it flies apart.
Otherwise, *ablation* with nukes is preffered wherein nukes are detonated ahead of the asteroid, heating the surface to offgass and deflect trajectory (velocity). There are many other schemes, such as gravity 'tractors' but that takes time. Think *Apophis* 2004 MN4, aka 99942.
Of course, the same idea that can deflect such things can redirect them for malice.
(no links, nobody here reads them anyways cause ya'll already know...)
Dayum, Greg... apologies about the 'already know'. I thought I was responding to Orac's walls-o-tripe.