Sunday, 23 May 2010

Ice on the surface of an asteroid: the astronomers’ coelacanth?

Using NASA’s infrared telescope on Mauna Kea, astronomers found surface water ice on an asteroid. Image courtesy of Wikipedia.

Joel Kontinen

What does the coelacanth Latimeria chalumnae have in common with surface ice on an asteroid called 24 Themis? According to an article in Nature, both are relics of the past and should no longer exist.

The coelacanth is a living fossil. The first live Latimeria chalumnae was found in 1938. The surface ice on 24 Themis was discovered much later.

Recently, Nature published two letters on the surface ice of the asteroid. 24 Themis orbits the Sun at about 3.2 astronomical units (AU) from it in the main asteroid belt between Mars and Jupiter. (1 AU is the distance from Earth to the Sun.)

There is still surprisingly much water ice on the surface of 24 Themis. However, astronomers who believe in billions of years would not expect ice to remain on the relatively warm surface of an asteroid so they have had to think hard to find explanations for this ”anomaly”, such as (a) ice continually rises to the surface from deeper in the asteroid or (b) impacts with other asteroids keep the surface covered by ice.

A much more logical explanation would be to acknowledge that 24 Themis is not billions of years old. Like comets, Saturn’s moon Titan and Mercury’s magnetic field, 24 Themis speaks of a young solar system.


Campins, Humberto & al. 2010. Water ice and organics on the surface of the asteroid 24 Themis. Nature 464:7293, 1320-1321 (29 April).

Hsieh, Henry H. 2010. A Frosty Finding. Nature 464:7293, 1286-1287 (29 April).

Rivkin, Andrew S. and Joshua P. Emery. Detection of ice and organics on an asteroid surface. Nature 464:7293, 1322-1323 (29 April).