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Mars Asteroid Impact More Likely Than Before
sheldie writes "The probability of asteroid 2007 WD5 impacting Mars has been revised following further observations. The chance of impact has increased from 1.3% to 3.9%" This is a follow-up to earlier coverage of this asteroid from last week.
The more it moves, however, the higher the precision of the measurements can be. So as time progresses, the astronomers will be able to reduce the circle of uncertainty.
John
Accuracy of measurements, mainly.
Also, regarding Jupiter and Shoemaker-Levy 9: Jupiter is a much larger target with a much larger gravitational field. In fact, Comet Shoemaker-Levy 9 was actually orbiting Jupiter (not the Sun), and it was easy enough to see that its orbit was decaying. That fact alone means a collision was near certain.
Remember how these things work - they made a few observations, from which they made a cone through which they're 95% (or whatever) sure that the asteroid will pass. Mars filled up about 1.3% of that cone, and so they can say that there's a 1.3% chance that Mars will be hit by the asteroid.
A few days later, with better observations, the cone shrinks, and now Mars takes up 3.9% of the cone. As the cone shrinks, Mars will continue to consume a larger and larger portion of it, right up until the time (maybe) that the cone shrinks outside of Mars and they determine that there will be no impact.
So remember, this is not unusual, and *every* non-impact event follows this pattern: Scientists find potential impact. Impact probability increases. Impact probability increases. (maybe a few more repetitions, too) Suddenly, they decide that it's not going to hit, and impact probability goes to zero.
-Rob
Biblical fiscal responsibility
2007 TU24 - approaching
Approximate diameter: 319 meters (H=20.131)
Closest Earth approach: 1.44 LD at 0826 UTC on 29 Jan. -----
Inside ten LD of Earth: 24 Jan. until 3 Feb.
Inside Earth's Hill sphere: 27 to 31 Jan.
Closest Moon approach: 2.20 LD at 1533 UTC 29 Jan.
Data based on: JPL SSD orbit solution #13 downloaded 6 Dec.
based on 87 observations spanning 54 days
Optical observation: observed from 13 locations during 53.8661 days
discovered at 0626 UTC on 11 Oct. by the Catalina Sky Survey
last observed at 0313 UTC on 4 Dec. by the Spacewatch 1.8m telescope
This shows that a rock 319m in diameter will pass by the Earth on January 29th 2008, it's closest point will be about 1.4 times the moons orbit or about 357,000 miles. This is VERY VERY close.
Regards
Ed Almos
The more corrupt the state, the more numerous the laws. - Tacitus, 56-120 A.D.
What "science" do you have in mind? Mars has already a bazillion craters to look at
But no FRESH ones. All the craters are millions of years old and have been weathered and contaminated. A fresh divot would expose deeper soils and rocks that have not previously been exposed to the atmosphere.
Also, there are things to learn about the mechanics of larger impacts on Earth-like planets. Since comparisons have been drawn between this and the Tunguska explosion, perhaps studying this will help prove or disprove that theory.
=Smidge=
Actually, since the asteroid's mass is negligible to that of the planets, its mass is irrelevant to its trajectory as it can be considered a test particle. We only need to know six pieces of information - three spatial coordinates, and three velocity components. It's easy to measure four of these very accurately, but the radial distance and velocity of the asteroid with respect to us are harder. These are where the majority of the uncertainty comes from.
The same object missed us by 5 million miles -- about 1/8 the separation between Earth and Mars orbits -- two months ago and we didn't see it until two weeks later.
rj