How do they know this?

Question

I just read Yahoo's version of the meteor that may hit Mars.

http://news.yahoo.com/s/ap/20071221/ap_on_sc/mars_asteroid

In the article, it says, "Scientists tracking the asteroid, currently halfway between Earth and Mars..." - Halfway between Earth and Mars? How do they know it won't hit Earth, then?

I meant asteroid, sorry.

Answer 1

2007 WD5 was discovered 11/20/07. 25 observations have been made to date. Using these observation measurements, NASA jpl incorporates them into computer programs which then calculate the asteroid's trajectory orbit. Calculations are updated with each observation to refine the projected orbital path.

2007 WD5 has an orbit that takes it from the asteroid belt between Mars and Jupiter to just outside of Earth's orbit. Since the orbital path of 2007 WD5 remains outside the limits of Earth's orbit, the two objects can not collide unless the orbital path of 2007 WD5 was to be deflected.

As it is now, 2007 WD5 has a Minimum Orbit Intersection Distance of .0321 AU of Earth. This is as close as it could get. Although it was not discovered until 11/20/07, it actually came .0479 AU distance from Earth on 11/2/07. This is evidence that not all NEO's are detected early. The asteroid has an orbit of about 4 years. This does not mean that it will come close to Earth every 4 years as Earth would not be in the same point of it's own orbit.

You can see the orbit of 2007 WD5 here:

Answer 2

They know the orbit of Mars to very high precision, and can determine its position in the future very accurately.

They know the orbit of this asteroid. Not as accurately as Mars, but accurate enough.

By calculating the orbits in the future, they can see when the two bodies might collide. They can determine that it won't hit Earth the same way.

Answer 3

Dude halfway between the earth and mars is nothing to be scared of there are heaps of asteroids halfway between earth and the moon. Yeah as for how we know as the guy above said scientists track the object in the sky few times and calculate its orbit pretty accurately.

Answer 4

if you make three separate observations of an object in the solary system and measure where it is in the sky those three times, you can begin to construct the orbit of that object with a fair degree of accuracy. The more observations you make, the more accurate the projected orbit. With modern telescopes and computers, we can make many observations from many places on the earth accurately and quickly compute an orbit. So you can be confident this prediction is accurate.

Answer 5

If it is close to mars it has already passed through the orbit of the earth,if it misses mars mercury will be next.
If it misses mercury then the next stop will be the sun.

Answer 6

Seems like you're in search of a simple answer. It's travelling in a certain direction. That direction is towards Mars, and not towards us on Earth. Is that simple enough for you????

Answer 7

thanks for that link, SCI..... of course, that makes it look like that rock came awfully close to EARTH first!!!... that's quite a nice JAVA applet to see how the orbits are going to cross.....

so, in answer to the question, looks like it snuck up on us, whizzed right by without anyone raising an alarm until now.... and that's scary......even if it was further away than the moon... it WAS, wasn'tn it????.....

Answer 8

Dang! And I had my "Asteroid-Mitt" ready to catch it, lmao.

Answer 9

they just add the
beetween earth and mars thing
to add more info
and make them seem smarter ^-^