Is it really possible to land a space craft on an asteroid or meteor

i dont remember but i think i read or heard that nasa wants to land a robot or ship on an asteroid or meteor to study them or something

is that even possible

if they land on it wouldnt they drift off into space

An asteroid, yes. It's been done. JAXA's Hayabusa probe landed and returned samples from 25143 Itokawa. Its not like their motion is unpredictable. It's no different from landing on a REALLY small planet or moon, really.

Landing on a meteor would be tricky, though, since the term only applies to bodies which have entered atmosphere but not impacted. As such bodies are in varying stages of disintegration from atmospheric friction, attempting a rendezvous wouldn't be wise.

The answer is yes. Think in simpler terms: You are going along the freeway at 75 mph and you want to talk to your friend in the next car. The speed between you and your friend is at or near zero as you hand him his soda which he forgot. the both of you are still going along the freeway at 75 mph but you can reach out and hand him the drink because between the two of you the speed is zero.

Same thing happens in Space - the Spacecraft matches the speed of the asteroid and 'sets down'. Sure enough they are both going at (pick some speed) through Space but to each other that speed is zero.

Another example: The Shuttles that docked with the Space Station use the same principal - but remember they are both traveling at 18,000 mph around the Earth just to stay in orbit above the Earth.

There can be landings on asteroids. As already mentioned, trajectories, velocities and other calculations would have to be performed in order to make it a safe and practical landing (manned or unmanned). The gravity of these typically small bodies likely will not be enough to keep a vessel down under the small amount of weight the low gravity is causing so some help may be needed such as a method of staking a vessel and keep people, equipment and otherwise grappled or tethered to the surface and/or spacecraft.

But basically, yes, we can land on asteroids or comets. We have the science to do it.

You have a good point. Only the largest asteroids would have enough gravity to hold a ship or probe. But there are a few large ones.

For smaller asteroids, a "landing" is really matching the asteroid's trajectory, at zero distance. But we can still call it a "landing", if we want to.

Well, ..., we already did on February 12 2001 by landing the Near space on the Asteroid EROS. See the link below.