Supernova iron found on the moon

moon
This is a composite image of the lunar nearside taken by the Lunar Reconnaissance Orbiter in June 2009, note the presence of dark areas of maria on this side of the moon. Credit: NASA

Approximately two million years ago a star exploded in a supernova close to our solar system: Its traces can still be found today in the form of an iron isotope found on the ocean floor. Now scientists at the Technical University of Munich (TUM), together with colleagues from the US, have found increased concentrations of this supernova-iron in lunar samples as well. They believe both discoveries to originate from the same stellar explosion.

A dying star ends its life in a cataclysmic explosion, shooting the majority of the star's material, primarily new chemical elements created during the explosion, out into space.

One or more such supernovae appear to have occurred close to our solar system approximately two million years ago. Evidence of the fact has been found on the earth in the form of increased concentrations of the iron isotope 60Fe detected in Pacific ocean deep-sea crusts and in ocean-floor sediment samples.

This evidence is highly compelling: The radioactive 60Fe isotope is created almost exclusively in supernova explosions. And with a half-life of 2.62 million years, relatively short compared to the age of our solar system, any radioactive 60Fe originating from the time of the 's birth should have long ago decayed into stable elements and thus should no longer be found on the earth.

Lunar samples from the Apollo missions

This supernova hypothesis was first put forth in 1999 by researchers at the Technical University of Munich (TUM) who had found initial evidence in a deep-sea crust. Now their claim has received further substantiation: Physicists at the TUM and their colleagues from the US have succeeded in demonstrating an unusually high concentration of 60Fe in lunar ground samples as well.

The samples were gathered between 1969 and 1972 during Apollo lunar missions 12, 15 and 16, which brought the lunar material back to earth.

It's also conceivable that 60Fe can occur on the moon as the result of bombardment with cosmic particles, since these particles do not break up when colliding with air molecules, as is the case with the earth's atmosphere. Instead they directly impact the lunar surface and can thus result in transmutation of elements. "But this can only account for a very small portion of the 60Fe found," explains Dr. Gunther Korschinek, physicist at TUM and scientist of the Cluster of Excellence Structure and Origin of the Universe.

Deposits of newly produced stellar matter

"We therefore assume that the 60Fe found in both terrestrial and lunar samples has the same source: These deposits are newly created stellar matter, produced in one or more supernovae", says Dr. Korschinek.

Since the moon generally provides a better cosmic record than the earth, the scientists were also able to specify for the first time an upper limit for the flow of 60Fe that must have reached the moon. Among other things this also makes it possible for the researchers to infer the distance to the supernova event: "The measured 60Fe-flow corresponds to a supernova at a distance of about 300 light years," says Korschinek. "This value is in good agreement with a recently theoretical estimation published in Nature."

The were investigated using the high-sensitivity accelerator mass spectrometer of the Maier-Leibnitz Laboratory near Munich.


Explore further

Supernovae showered Earth with radioactive debris

More information: L. Fimiani et al. Interstellar on the Surface of the Moon , Physical Review Letters (2016). DOI: 10.1103/PhysRevLett.116.151104
Journal information: Physical Review Letters , Nature

Citation: Supernova iron found on the moon (2016, April 14) retrieved 25 April 2019 from https://phys.org/news/2016-04-supernova-iron-moon.html
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Apr 14, 2016
Well done for finding a correlation between earth and moon samples, though it shouldn't come as a surprise - we are sharing the same environment after all.

If they carry on looking I'm sure they will find more.

Apr 14, 2016
The solar system is young not old. Time to throw away the 4.5 billion
year nonsense and start believing the observations..and yes the
earth is no longer flat!

Apr 15, 2016
@blazmotronic: Never mind that the same methods that gets the 2 Myrs age in an Earth rock sequence and in Moon material gets tha 4.5 billion year age from many independent sources.

'Nonsense' and 'throw away', really!? Not as long as facts matter.

[The Earth hasn't been flat since the Hellenistic period. That is 2,5 kyrs of knowing better. [ https://en.wikipe...at_Earth ] ]

Apr 15, 2016
I thought all iron was from a supernova. I guess this isotope is created by the explosion rather than just released by. Someone want to tell me that not all gold is from a supernova? Getting mad at headlines but learning stuff all the same.

Apr 17, 2016
@EF: It is complicated. A massive star that burns sequential elements in shells stops with silicon burning into Fe and Ni as well. Such a star ends up in a supernova, so it is perhaps morally correct to call the latter the origin of all Fe (and some Ni). [ https://en.wikipe..._process ]

Apr 17, 2016
Thanks Tj_b_g_l. I appreciate your patience.

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