A New Twist to Dating an Asteroid

Aug 02, 2005

It turns out you can’t judge an asteroid by its cover, according to a recent study in the journal Nature. Or at least you can’t accurately date a certain asteroid called 433 Eros by counting the impact craters on its surface -- the traditional method for determining an asteroid’s age.

Peter Thomas, a senior research associate in astronomy at Cornell University and lead author on the paper, and Mark Robinson, research associate professor of geological sciences at Northwestern University, analyzed images of Eros gathered four years ago by the Near Earth Asteroid Rendezvous mission. The mission mapped the 20-mile-long, potato-shaped asteroid and its thousands of craters in detail. The two researchers focused on a large impact crater, known as the Shoemaker crater, and a few unusual crater-free areas.

In the Nature article, Thomas and Robinson show that the asteroid’s smooth patches can be explained by a seismic disturbance that occurred when a meteoroid crashed into Eros, shaking the asteroid and creating Shoemaker crater. The shaking caused loose surface material to fill some small craters, essentially erasing craters from approximately 40 percent of Eros’ surface and making the asteroid appear younger than its actual age.

The fact that seismic waves were carried through the center of the asteroid after the impact shows that the asteroid’s interior is cohesive enough to transmit such waves, say the authors. And the smoothing-out effect within a radius of up to 5.6 miles from the 4.7-mile Shoemaker crater -- even on the opposite side of the asteroid -- indicates that Eros’ surface is loose enough to get shaken down by the impact.

Asteroids are small, planet-like bodies that date back to the beginning of the solar system, so studying them can give astronomers insight into the solar system’s formation. And while no asteroids currently threaten Earth, knowing more about their composition could help prepare for a possible future encounter. Eros is the most carefully studied asteroid, in part because its orbit brings it close to earth.

Thomas and Robinson considered various theories for the regions of smoothness, including the idea that ejecta from another impact had blanketed the areas. But they rejected the ejecta hypothesis when calculations showed an impact Shoemaker’s size wouldn’t create enough material to cover the surface indicated. And even if it did, they add, the asteroid’s irregular shape and motion would cause the ejecta to be distributed differently. In contrast, the shaking-down hypothesis fits the evidence neatly.

Source: Cornell University

Explore further: Russia launches British comms satellite into space

add to favorites email to friend print save as pdf

Related Stories

Gullies on Vesta suggest past water-mobilized flows

Jan 23, 2015

(Phys.org)—Protoplanet Vesta, visited by NASA's Dawn spacecraft from 2011 to 2013, was once thought to be completely dry, incapable of retaining water because of the low temperatures and pressures at its ...

Telescope to seek dust where other Earths may lie

Jan 22, 2015

The NASA-funded Large Binocular Telescope Interferometer, or LBTI, has completed its first study of dust in the "habitable zone" around a star, opening a new door to finding planets like Earth. Dust is a ...

Stepping stones to NASA's human missions beyond

Jan 21, 2015

"That's one small step for (a) man; one giant leap for mankind." When Neil Armstrong took his first steps on the moon, many strides came before to achieve that moment in history. The same is true for a human ...

Recommended for you

Japan launches new spy satellite

14 hours ago

Japan on Sunday successfully launched a back-up spy satellite, its aerospace agency said, after cancelling an earlier lift-off due to bad weather.

NASA launches satellite to measure soil moisture

14 hours ago

NASA on Saturday launched a new Earth-observing satellite that aims to give scientists high-resolution maps showing how much moisture lies in soil in order to improve climate forecasts.

Planck: Gravitational waves remain elusive

Jan 30, 2015

Despite earlier reports of a possible detection, a joint analysis of data from ESA's Planck satellite and the ground-based BICEP2 and Keck Array experiments has found no conclusive evidence of primordial ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.