Moon rocks reveal surprising meteorite history

SHRIMP-2 Curtin University

Associate Prof Nemchin's discovery challenges the long-held view that there was a single spike in huge meteorite impacts 3.9 billion years ago. 

Credit: Curtin University

Alexander Nemchin, a WA geologist, analyzing lunar rock samples collected during the Apollo missions has uncovered evidence of a huge meteorite strike 4.2 billion years ago.

Curtin University Associate Professor Alexander Nemchin made the discovery when he dated a section of rock from the Moon that melted in heat of the meteorite impact.

The object that hit the Moon was probably tens of kilometers across and would have left a crater several hundred kilometers wide.

Associate Prof Nemchin says the strike happened at least 300 million years before the youngest known lunar impact basins and his discovery challenges the long-held view that there was a single spike in huge impacts 3.9 billion years ago.

He says this period of intense meteorite bombardment, which would have affected both the Moon and the Earth, was previously thought to be a one-off event.

"A few years ago we started to see evidence that it's probably not quite the case," Nemchin says.

"It's possible that there are some impacts not related to this 3.9 [billion years] spike … there are some that happened much earlier.

"It has implications for a number of things including how life evolved on Earth."

Nemchin analysed the moon rock using SHRIMP, an ion probe instrument, at Curtin University, which allows researchers to determine the age of tiny amounts of rock by examining the atoms that make up the sample.

He was able to borrow the rock, which was collected from the rim of North Ray crater during the Apollo 16 mission, because of NASA's relatively open approach to the use of moon rocks for scientific research.

"All you need is to have record of doing scientific research, you need to demonstrate that you've got a way to keep the samples safe and you know how to work with small, rare samples," Nemchin says.

"It's really very open in many ways."

Nemchin says currently the best explanation for any increase in meteorite impacts throughout the Solar System 3.9 billion years ago is that some planets were thought to be displaced from their normal orbits at that time.

He says the movement of Jupiter and Saturn, with their huge mass, destabilised Neptune and sent smaller asteroids and comets "randomly flying around" in the Solar System.

"Of course when they go all over the place they start hitting all the other planets," Nemchin says.

3D printers could use Moon rocks to make supplies, say scientists

Future Moon colonists should be able to use lunar rocks to create tools or spare parts, according to a study.

US researchers have used a 3D printer to make small objects out of melted simulated lunar rocks.

They say the technique could help future missions to minimise the weight and the expense of carrying materials into space as a digital file would be enough.

But one expert says such a printer would have to be extremely precise.

In 2010, Nasa asked a team from Washington State University to see whether it was possible to use lunar rocks for 3D printing.

It supplied the researchers with simulated Moon rocks, or lunar regolith simulant, containing silicon, aluminium, calcium, iron and magnesium oxides.

Many hundreds of kilograms of Moon rocks were collected during Nasa missions, but the scientists did not use them because they are considered a national treasure in the US.

Lunar regolith simulant is commonly used for research purposes at Nasa.

"It sounds like science fiction, but now it's really possible," said Prof Amit Bandyopadhyay, the lead author of the study, published in the Rapid Prototyping Journal.

His team created simple 3D shapes by sending a digital file or scan to a printer which then built the items layer by layer out of melted lunar regolith, fed via a carefully controlled nozzle to form a shape. The process is known as "additive manufacturing".

A laser was used to melt the material.

"As long as you can have additive manufacturing set up, you may be able to scoop up and print whatever you want. It's not that far-fetched," said Prof Bandyopadhyay.

The research demonstrates the latest advances in 3D printing technology, which is already in use in medicine, fashion, car manufacturing and other industries.