[meteorite-list] Few Asteroids Are Worth Mining, Suggest Harvard Study

[Ron Baalke]

http://www.bbc.co.uk/news/science-environment-25716103

Few Asteroids Are Worth Mining, Suggest Harvard Study
By Paul Rincon
BBC News
13 January 2014 

A new study might contain some bad news for companies hoping to mine asteroids 
for their valuable ores.

In the last couple of years, start-ups - including one backed by Sir Richard 
Branson - have announced plans to extract resources from space rocks.

But calculations by Dr Martin Elvis suggest our cosmic neighbourhood might 
not be such a treasure trove after all.

The Harvard astrophysicist suggests just 10 near-Earth asteroids might 
be suitable for commercial-scale mining.

But Eric Anderson, co-founder of asteroid mining company Planetary Resources, 
told BBC News that the values quoted in the study were off - conservatively 
- by a factor of 100.

Dr Elvis, from the Harvard-Smithsonian Center for Astrophysics in Cambridge, 
US, has developed an equation that estimates the number of asteroids in 
the Solar System that could be exploited in a cost-effective way.

His research paper is in press at the journal Planetary and Space Science 
and has been published on the pre-print server Arxiv.org.

But other researchers said there were still many uncertainties about what 
was in the many thousands of sizeable space rocks near our planet.

In 2012, Planetary Resources, backed by billionaire investors including 
Hollywood director James Cameron as well as Google executives Larry Page 
and Eric Schmidt, unveiled their vision of using robotic spacecraft to 
squeeze the chemical components of fuel as well as minerals out of asteroid 
rocks.

Several months later, the company was joined by a competitor - Deep Space 
Industries - which plans to use low-cost spacecraft called Fireflies and 
Dragonflies to reconnoitre and return samples from near-Earth asteroids.

Advocates of asteroid mining say it could turn into a trillion-dollar 
business, but some experts have been sceptical of the idea.

Concentrating efforts

In the latest study, Dr Elvis worked out the factors that would make an 
asteroid commercially viable to mine and what fraction of known space 
rocks met these requirements. Though he emphasised large uncertainties 
in the values and called for more thorough surveys of what's out there.

He assumed that mining operations would want to focus on iron-nickel asteroids 
(known as M-type), considered the most promising targets for finding so-called 
platinum-group metals - which include  platinum, along with iridium, palladium 
and others.

These are rare in the Earth's crust because they dissolve in molten iron, 
instead being mainly concentrated in the planet's core. Platinum and palladium 
are the most economically important, having a wide range of uses in industry. 
But according to the analysis, just 1% of near-Earth asteroids are rich 
in these elements.

In addition, suitable asteroids also need to be relatively easy to reach, 
further narrowing the pool by ruling out all but the nearest objects to 
Earth. The operative parameter here is delta-v - the change in velocity 
needed to send mining equipment to the target and return with a larger 
mass of ore.

The size of the target is also a factor; the paper suggests it wouldn't 
be worth mining asteroids smaller than about 100m because the total value 
of the ore they would produce wouldn't be enough to cover the costs of 
a space mission.

However, Dr Elvis points out that the ore values in his analysis ranges 
from a low of $800m to $8.8bn.

"Such a large range of values could greatly change the profitability of 
a venture, making more accurate assays necessary," he explained.

Broader range

But Eric Anderson pointed to what he said were key errors in the study.

"Number one, the author points to an assumption of only wanting to go 
to M-type asteroids," he explained.

"Assuming we were only going after platinum-group metals, the most platinum-rich 
asteroids are the C-class ones." Bits of these asteroids are known as 
carbonaceous chondrites when they fall to Earth.

In addition, Planetary Resources' engineers were prepared to include objects 
that required a delta-v of 7km/s, a more ambitious limit than the 4.5km/s 
used in Dr Elvis' study.

"I think the study is probably off by a factor of 100, conservatively, 
and I think it's off by a factor of 1,000 optimistically," Mr Anderson 
told BBC News.

He added: "We've been studying this with some of the brightest people 
in the world for the last three years. We are intimately familiar with 
the risks and other factors.

"We have only discovered 1% of the asteroids in the Solar System - and 
we are discovering them at a larger and larger rate. We discover two or 
three asteroids a day. If we get from 1% to 10%, then the 650,000 asteroids 
we have discovered jumps to 6.5 million."

The analysis also looked at the number of asteroids that could be profitably 
mined for water - which could be used in space for life support or separated 
into hydrogen and oxygen for rocket fuel. The number of suitable water-bearing 
asteroids larger than 100m was around 18.

Dr Elvis told BBC News: "I want to stress that my paper does not mean 
that there is no commercial future for asteroid mining. It does mean that 
gold mines are rare, which shouldn't be too surprising. Not every mountain 
on Earth hides a fortune, and not every flying mountain in space will 
either."

Still unknown

Prof Alan Fitzsimmons, from Queen's University Belfast, who was not involved 
with the study, said the calculations were "plausible", but that he would 
have placed even more emphasis on the uncertainties.

"The make-up of small Near-Earth asteroids is still relatively unknown," 
he told BBC News.

"There are large uncertainties in the total number of platinum group-rich 
asteroids that come near the Earth. This is because it is still difficult 
to unambiguously determine the mineral makeup of small asteroids.

"We know they exist, as pieces are found as meteorites on Earth. The small 
asteroid that formed meteor crater in Arizona some 50,000 years ago was 
one such object."

In his paper, Dr Elvis wrote: "The apparently limited supply of potentially 
profitable [near-Earth objects] argues strongly for an accelerated rate 
both for discovery and especially for characterisation, which is lagging 
badly behind."

Prof Fitzsimmons added: "All-in-all, asteroid mining may be a plausible 
future space industry. But it would require significant capital investment 
to start such an industry. The practical problems of mining, refining 
and transport back to Earth are still unsolved right now."