If an asteroid,say the size of Texas,hit Earth,what would it look like overhead,just before the collision???

Question

Say I am next to the point of impact,looking up at the bright blue sky,but then I see???

Answer 1

There are very few asteroids the size of Texas right now. Early in the birth of the solar system, however, there were thousands of them. Based purely on probability, it is estimated during the first 400-500 million years after the formation of the Earth, the Earth was hit about 3-4 times by an asteroid the size of Texas.

A rock the size of Texas is immense, well over 100 times larger than the rock that took out the dinosaurs, large enough to become spherical in shape. Contrary to what you might expect, even though it's moving about 25K mph, the shear size would make the asteroid appear to move very slowly. You'd see the asteroid a day or so before it hit - a point of light at first, growing larger and larger. A couple of hours before it hit it would start to take shape - maybe 10 minutes before it hit it would look as large as the moon. Seconds before impact you would see a monstrous ball rolling slowly over the horizon.

Unlike a smaller asteroid, the air directly under the asteroid could not move out of the way fast enough to melt the rock or create the white glow. Instead, the air would compress. And because over 90% of the asteroid would still be outside of the atmosphere when the initial impact occurred, the last thing you'd feel is the atmosphere reaching thousands of pounds per square inch as the asteroid compressed the air (and you) directly underneath it.

Unlike a smaller asteroid, the impact itself would last several seconds, maybe even minutes. Most of the asteroid would fracture and rebound into space with the Earth's mantle as the incredible kinetic energy is converted into heat. The Earth's crust and upper mantle would start to peel like the skin of an orange and vaporize. Entire continents would peel and hurled a hundred miles into space before vaporizing in the heat. The melted crust and asteroid would form a wall of "rock vapor" - superheated, vaporized rock - that extended well above the atmosphere, maybe 200-250 miles high. Slowly the rock vapor would circle the Earth. No matter where you were in the world, the last thing you'd see is a 200-mile high wall of superheated, 15,000 degree vaporized rock screaming at you at the speed of sound. Within 24 hours, the entire globe would be engulfed.

The rock vapor would remain for about a year. Temperatures on the Earth's surface would remain above 500C degrees for centuries. During that time the atmosphere and oceans will boil and vaporize. Even the salt at the bottom of the seas would melt and vaporize. After about a thousand years the temperatures would drop to the point that the water vapor, trapped by Earth's gravity, would condense; and in a very short time - maybe less that 100,000 years - the rains will fall and the oceans will fill again. Although the surface of the Earth would be sterilized, it is possible that microbes living several miles within the bedrock, on the opposite side of the globe from the impact, may survive to repopulate the oceans.

Again, this happened 3-4 different times, about 4 billion years ago.

Answer 2

There are no asteroids as big as Texas so the question does not arise, You cannot pluck figures out of thin air like this.

Dimensions of Texas:
Width 773 miles (1,244 km)
Length 790 miles (1,270 km)

The biggest asteroid by far is 1 Ceres and its diameter is approx 900-1000 kilometres. Only 3 other asteroids have a girth of over 500 kilometres and eveything else is a relative flyweight at 325 kilometres or less,

The 19 largest known asteroids
Name Diameter (km)
1 Ceres 975×909
4 Vesta 578×560×458
2 Pallas 570×525×500
10 Hygiea 500×385×350
511 Davida 326
704 Interamnia 317
52 Europa 360×315×240 *
624 Hektor 370×195
15 Eunomia 330×245×205
3 Juno 290×240×190
87 Sylvia 261
31 Euphrosyne 256
16 Psyche ~280×230×190
65 Cybele 237
107 Camilla 340×230×140
121 Hermione 265×180×180
9 Metis 235×195×140
324 Bamberga 229
24 Themis 228

* not the same thing as Europa, the moon of Jupiter which is much bigger (diameter 3122 kilometres).

They all have stable orbits that do not bring them closer to Earth than Mars ever gets, We know (as of September 17th 2006) of 342,538 asteroids but as of August 31, 2006, only 4,130 are classed as Near Earth Objects (NEOs), of which there are 792 NEOs which are classified as potentially hazardous asteroids.

SO: WHAT SIZE ARE THE ASTEROIDS THAT DO APPROACH THE EARTH?

Well, the asteroid causing ripples of concern about a possible 2029 or 2036 collision with Earth, 99942 Apophis weighs in at a mere 320 metres in diameter.

4179 Toutatis which closely approached Earth on September 29th, 2004 is 4.5×2.4×1.9 kilometres in size,

The second largest NEO, 433 Eros (not the same thing as 136199 Eris) is 13×13×33 kilometres in size,

An asteroid is considered a Potentially Hazardous Asteroid (PHA) if its Minimum Orbit Intersection Distance (MOID) with respect to Earth is less than 0.05 AU and its diameter at least 150 metres (nearly 500 ft). This is big enough to cause unprecedented regional devastation for a land impact or the threat of a major tsunamai for an ocean impact, if it were to hit the Earth. Such impact events occur on average once per 10,000 years or less.

So such close encounters with PHAs if they occur will be unpleasant but nowhere as melodramatic as your imagination is telling you they might be.

With NASA, the European Space Agency and others co-operating in a project called Spaceguard to pool information on possible impacts of NEOs with the Earth or the Moon, and intensively investigate orbits that make the asteroid a PHA, to be able to predict their movements with precision, there would be reasonable advance warning of an imminent hazardous approach, such that strategies to deflect the asteroid from its path can be decided on, something that was simply never available before.

Damaging impacts should therefore be far less frequent than once in 10,000 years, as we can now predict with greater precision and have the means to prevent them from happening,

Previously, we just had to sit there and wait to be hit. That is no longer the case,

Answer 3

Hi. It would be a strange sight. The first effect (after entering the atmosphere) would be heating due to the Diesel effect (compression of the air to a high temperature). Next would come a "pancaking" of the front surface of the asteroid due to high pressure. This would cause an intense glow. You would feel the effects as the pressure wave hit you at Mach 1 (or sooner if the asteroid was traveling faster than this speed). Blue sky would turn to white heat just before you were vaporized, quite painlessly due to the speed.

Answer 4

Texas is about 900 miles across. At the instant it enters the Earth's atmosphere, i.e., 60 miles up, it will cover about 165 degrees across the sky, or about 92%^2 = 83% of the entire sky.

At 25,000 mph, the amount of clear sky will continue to diminish for another 8.6 seconds.

Answer 5

Imagine what a fly sees just before it gets swatted but forget the bright blue sky.

Answer 6

Extremely bright light, asteroid heats up and "glows" as it passes through the atmosphere. Will seem much brighter than the sun.

Answer 7

Probably like Texas.

Answer 8

I wouldn't know. I'd be hiding under my bed, crying like a little girl.

Answer 9

A lone star.

Answer 10

A giant rock ?