Is this meteorite a piece of Mercury?

Feb 04, 2013 by Jason Major, Universe Today
The largest fragment of meteorite NWA 7325. (Credit: Stefan Ralew / sr-meteorites.de

Pieces of the Moon and Mars have been found on Earth before, as well as chunks of Vesta and other asteroids, but what about the innermost planet, Mercury? That's where some researchers think this greenish meteorite may have originated, based on its curious composition and the most recent data from NASA's MESSENGER spacecraft.

NWA 7325 is the name for a fall that was spotted in southern Morocco in 2012, comprising 35 fragments totaling about 345 grams. The dark green stones were purchased by meteorite dealer Stefan Ralew (who operates the retail site SR Meteorites) who immediately made note of their deep colors and lustrous, glassy exteriors.

Is this meteorite a piece of Mercury?

Ralew sent samples of NWA 7325 to researcher Anthony Irving of the University of Washington, a specialist in meteorites of planetary origin. Irving found that the fragments contained surprisingly little iron but considerable amounts of magnesium, aluminum, and calcium silicates—in line with what's been observed by MESSENGER in the surface crust of Mercury.

And even though the ratio of calcium silicates is higher than what's found on Mercury today, Irving speculates that NWA 7325 could have come from a deeper part of Mercury's crust, excavated by a powerful and launched into space, eventually finding their way to Earth.

In addition, exposure to for an unknown period of time and shock from its formation could have altered the meteorite's composition somewhat, making it not exactly match up with measurements from MESSENGER. If this is indeed a piece of our Solar System's innermost planet, it will be the first Mercury meteorite ever confirmed.

But the only way to know for sure, according to Irving's team's paper, is further studies on the fragments and, ultimately, sample returns from Mercury.

Irving's team's findings on NWA 7325 will be presented at the 44th Lunar and Planetary Science Conference to be held in Houston, TX, on March 18-22.

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Sinister1811
2.2 / 5 (10) Feb 04, 2013
Very interesting. Although most of these meteorites from Mercury would fall inwards towards the sun, there's no doubt that the odd one here and there could escape into outer orbits and possibly end up on Earth, though the chances are pretty slim.
Szkeptik
5 / 5 (2) Feb 04, 2013
Very interesting. Although most of these meteorites from Mercury would fall inwards towards the sun, there's no doubt that the odd one here and there could escape into outer orbits and possibly end up on Earth, though the chances are pretty slim.


Well, most asteroids would impact its far side, so what ever flies out will probably do so towards higher orbits. However to make it to Earth's orbit it would need to acquire an impressive amount of extra orbital velocity.
meta-atem
2.3 / 5 (3) Feb 04, 2013
Very interesting. Although most of these meteorites from Mercury would fall inwards towards the sun, there's no doubt that the odd one here and there could escape into outer orbits and possibly end up on Earth, though the chances are pretty slim.


Well, most asteroids would impact its far side, so what ever flies out will probably do so towards higher orbits. However to make it to Earth's orbit it would need to acquire an impressive amount of extra orbital velocity.


Or launched into a fortuitous orbit that it could gain velocity from close encounters with the sun.
antialias_physorg
4.2 / 5 (5) Feb 04, 2013
Or launched into a fortuitous orbit that it could gain velocity from close encounters with the sun.

If you start with a certain velocity relative to the sun at a certain orbit then no matter which path you take around the sun you will not end up with more velocity when you hit that orbital distance again (swing by maneuvers don't work with the sun - only against bodies that move relative to the sun).

If that piece came from Mercury then it must have gotten the kinetic energy required to reach Earth orbit in the initial impact which hurled it off into space (or with a secondary impact along the way - which is rather unlikely)
meta-atem
2.3 / 5 (3) Feb 04, 2013
If you start with a certain velocity relative to the sun at a certain orbit then no matter which path you take around the sun you will not end up with more velocity when you hit that orbital distance again (swing by maneuvers don't work with the sun - only against bodies that move relative to the sun).

If that piece came from Mercury then it must have gotten the kinetic energy required to reach Earth orbit in the initial impact which hurled it off into space (or with a secondary impact along the way - which is rather unlikely)


Of course, I knew that (doh!). So then perhaps additional encounters with Mercury and eventually Venus? Is serendepity a valid variable when doing orbital mechanics?
Q-Star
3.4 / 5 (5) Feb 04, 2013
Of course, I knew that (doh!). So then perhaps additional encounters with Mercury and eventually Venus? Is serendepity a valid variable when doing orbital mechanics?


No serendipity is not a valid variable. That is why he took the trouble to doubt whether a secondary impact encounter might have happened. Anything that might have altered the trajectory after the initial conditions (at impact) would have been serendipitous.

The most likely initial condition was an impact which imparted enough momentum for it to later collide with Earth.

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