Martian Meteorite Gets NASA Mars Rover's Attention 94
coondoggie writes "NASA's Mars rover Opportunity will take a small detour on its current journey to check out what could be a toaster-sized iron-based meteorite that crashed into the Red Planet. NASA scientists called the rock 'Oileán Ruaidh,' which is the Gaelic name for an island off the coast of northwestern Ireland. The rock is about 45 centimeters (18 inches) wide from the angle at which it was first seen on September 16."
Re:Something is missing (Score:3, Informative)
In the ground, which is at an angle in this photograph that would either put it out of sight, or off frame?
Oileán Ruaidh (Score:2, Informative)
Oileán Ruaidh translates to red island.
Re:Something is missing (Score:5, Informative)
Destroyed by winds and soil erosion.
Re:Something is missing (Score:5, Informative)
http://michaelscomments.wordpress.com/2006/11/19/meteorite-hits-car/ [wordpress.com]
Look at the size of that rock. It didn't make a crater the size of a house, all it did was add an easy access hole to someones trunk. And roof.
I imagine by the time a rock that size passes through the atmosphere and survives, its moving slow enough to rebound off the surface, or, in this case, get stopped by a car.
Re:Something is missing (Score:5, Informative)
A) it's small. Small meteorites don't make much of a crater because their velocity is slowed much more than larger meteorites
B) the area that Opportunity is visiting has experienced substantial erosion on the bedrock surface, such that even if it did make a small dent in the surface, it could be eroded away by now. More durable rock types (such as the iron-nickel meteorites found previously, and also the hematite "blueberry" concretions that litter the surface) tend to accumulate on the surface as the softer rock is worn away. It's what geologists call a lag deposit [encyclopedia.com].
Incidentally, Opportunity has already moved a closer to the rock in question. The picture in the article was taken on Sol 2363 [nasa.gov], and there are now pictures downloaded to Sol 2367, such as this one [nasa.gov], and this one [nasa.gov]. The higher-resolution "Panoramic Camera" images aren't fully downloaded, but you can see the edge of the rock [nasa.gov]. Looks like the next download pass they should have some pretty good shots. Check the "raw images" page for the Opportunity Rover [nasa.gov] in the next couple of days and there should be plenty of closer shots.
Re:Why? (Score:3, Informative)
Re:Something is missing (Score:2, Informative)
In the BBC series Wonders of the Solar System [bbc.co.uk], this type of non-crater-producing Martian meteorite is used as possible evidence that Mars had a thicker atmosphere in the distant past when these meteorites impacted. It was in the Thin Blue Line [wikipedia.org] episode if I remember correctly.
Re:Something is missing (Score:3, Informative)
Rocks coming from space arrive at speeds from slightly less than escape velocity to much more than escape velocity*. A rock following the planet in a similar orbit may enter the planet's gravity well at a speed relatively near to 0, but by the time it hits atmosphere the relative speed will be very high. And a rock falling towards the sun on an elongated elliptical orbit that intersects the Earth's will be going extremely fast at the point it reaches the atmosphere.
The incident angle is more of a factor here. A direct descent through 100 km of progressively increasing density of air will have only a few seconds to decelerate and will make a much bigger dent than a grazing trajectory that goes through hundreds or thousands of km of atmosphere, losing speed sometimes to the point it's at terminal velocity. Although terminal velocity for a solid hunk of iron is going to be several hundred kph at least, which would make it as destructive as a cannonball.
If the meteor explodes due to atmospheric heating, pieces can go in any direction with any speed from the point of the explosion, so it might be possible for a rock to have a fairly small speed on impact with the ground.
But more likely the case for the martian meteorite here is that it hit at an oblique angle and bounced and rolled to where it sits now. Follow its track back and you'll likely find a fair sized hole that may or may not be round (impact craters are funny in that they come out round for a wide range of angles of impact).
* - Escape velocity for Earth is 11 km/s (about 25k mph).