Thread: How do astronomers determine the composition of non-luminous celestial bodies, such as asteroids?

For example, here is an asteroid https://ssd.jpl.nasa.gov/tools/sbdb_.../?sstr=2436724
Everyone was talking about it all the time, because this asteroid contains a large amount of platinum but how they knew it? What devices and methods are used for this?

Originally Posted by Kevin_Hall

For example, here is an asteroid https://ssd.jpl.nasa.gov/tools/sbdb_.../?sstr=2436724
Everyone was talking about it all the time, because this asteroid contains a large amount of platinum but how they knew it? What devices and methods are used for this?

Analysis of meteorites.

Originally Posted by exchemist

Originally Posted by Kevin_Hall

For example, here is an asteroid https://ssd.jpl.nasa.gov/tools/sbdb_.../?sstr=2436724
Everyone was talking about it all the time, because this asteroid contains a large amount of platinum but how they knew it? What devices and methods are used for this?

Analysis of meteorites.

Yes. Analysis of reflected light can determine if there is nickel-iron on the surface but it is analysis of meteorites that tells us that the presence of nickel-iron means the presence of platinum and other Platinum Group Metals. If there is nickel-iron there will be PGM's - it is like a signature that says "came from space"... based on 10's of thousands of meteorite samples. They are present at 10's of ppm up to over 100 ppm, mixed in (alloyed in) the nickel-iron; there is no expectation of finding high grade seams or nuggets based on how asteroids are thought to have formed. Making alloys is easy but unmaking them is difficult - but apparently the Mond Process can separate the iron and nickel and leave the mixture of the rest, to be refined further by other means. High PGM content is associated with high nickel content. The Nickel may have more $ value than the PGM's.

I expect 10's of thousands of samples still leaves room for finding things that are exceptional and rare - perhaps remnants of pre-solar system materials formed from ancient supernovae will be found eg native metals apart from nickel-iron mixtures, ie nuggets after all. But the presence in nickel-iron is something we can count on.

More recently, a new approach to analyzing the composition of asteroids involves bringing parts of them back to Earth for study in labs. While such research has been done with meteorites, 'primordial asteroids' have had only limited analysis. Samples were recently obtained and returned from the asteroid Ryugu.

These samples were excavated by the Japanese spacecraft Hayabusa2 in 2019, and returned to Earth in late 2020. Some results have been released so far, and a recent article in
Nature Astronomy provides additional data*.

Unmolested by entry into Earth's atmosphere and never contaminated by impacting the surface, the samples should provide unique insight as to their content, and how they were formed.


"A pristine record of outer Solar System materials from asteroid Ryugu’s returned sample"

* https://www.nature.com/articles/s41550-022-01745-5