A zombie comet, officially called asteroid 2015 TB125, zipped past Earth at 120 000 kph on 31 October 2015.

Zombie comets are "dead", having lost the ice that would vaporise to give them a "tail" as they near the Sun.

The comet, with a diameter of 610 m, came closer to us than the moon and is the nearest we’ve come to a disastrous hit by a space object in 10 years.

What's more frightening is that it was detected only three weeks before it rushed past us.



The zombie comet was detected and mapped by bouncing powerful radio signals off its surface using radar technology at the Arecibo Observatory in Puerto Rico. The weak returning signals were heard by the 300-m diameter Arecibo radio telescope.

Only two telescopes in the Southern Hemisphere are capable of detecting and mapping asteroids like this, and both are in Australia. It is unlikely that the new precursor telescopes for the Square Kilometre Array (SKA), including South Africa’s MeerKAT, will be used for this sort of ongoing project.

NASA says some 13 300 near-Earth asteroids have been detected. Of these, 875 are one kilometre in diameter, and about 1 600 are considered potentially hazardous asteroids, which may endanger the Earth.

For instance, the chances of being hit by an asteroid with a diameter of 600 m (like the Halloween zombie) is one in every 150 000 years, with an explosive force equal to three times all the nuclear weapons on Earth.  We were very lucky on 31 October 2015.

It is difficult to observe the largest of these planet killers, as space is vast and asteroids don’t give off signals. More to the point, there are currently too few big radio telescopes to detect and track asteroids, and no proven way to protect the Earth from impending disaster.  We need to have more telescopes around the world.  While there are a number in the northern hemisphere, big telescopes are needed in Southern Africa and South America.

In the midst of threat comes great opportunity.  There are riches in these cosmic rocks. Some asteroids are carbon-rich, made from hydrogen, carbon, and oxygen, and others are metallic, containing iron, nickel, gold or platinum, for example. In the not-too-distant future many of these planet killers could be mined if we can get to them before they hit Earth.

NASA announced in 2013 that they would identify, track and capture a 7 to 10-m diameter asteroid and tow it back to a safe lunar orbit for study in 2021. They are looking for a carbon-rich asteroid that they can extract water, oxygen and fuel from; setting in motion the asteroid-mining era.

In 2012 Prof. John Lewis, author of Mining the Sky: Untold Riches from the Asteroids, Comets, and Planets, and now a consultant to Planetary Resources, estimates that an asteroid called Amun 3554 was worth $20 trillion in platinum, iron, nickel, gold and cobalt.

Planetary Resources, a company started by Larry Page, Google founder and James Cameron, film director, proposes mining asteroids such as Amun 3554.  Amun 3554 is an asteroid of less than one kilometre in diameter that crosses the paths of both Earth and Venus around the Sun.

Many other companies have also entered the fray.  More companies need to be convinced to start towing asteroids to where they can safely be mined.  This is not the preserve of the USA and Russia alone.

Perhaps the answer to protecting Earth is to "detect and profit" ‑ to detect bodies in good time to mine their dangers out of existence while earning good revenue.

What should South Africa be doing to get in on this future job and wealth creation opportunity?

Building telescopes capable of transmitting, detecting and tracking asteroids (which will improve global preparedness for catastrophic events caused by asteroid strikes) as well as determining the composition of detected asteroids.  We need to use the expertise in astronomy that we are currently developing and maturing, and to expand and transform our deep mining expertise to include space mining.

Entry into space mining would be facilitated if South Africa were to build a 65-m class radio telescope capable of transmitting, detecting and tracking asteroids, two 0.5-m optical telescopes to increase detection ability, and a 2-m class infrared telescope with fast-tracking capabilities to assist in determining the composition of detected asteroids.

Research programmes in space mining will contribute to increased local mining productivity, via new technologies, and give South African mining companies a foothold in a very new and exciting arena of operations, SPACE.


About the author:

Dr MacLeod, PhD (Astronomy), MBA, is an expert in star formation and business consulting, who recently rejoined the staff at Hart RAO after a 19-year absence.