Solar Flare Helps Eros Reveal Its Past

By Keith Cowing
May 31, 2000
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Preliminary chemical composition data from the NEAR-Shoemaker spacecraft, now in orbit around asteroid 433 Eros, show Eros to be made of material unchanged from the earliest days of our solar system. Curiously, this data was provided courtesy of a large solar flare.

On 4 May 2000, a large solar flare lashed out across the solar system, bathing Eros with a 30 minute dose of X-rays. As a result of this large input of energy, Eros fluoresced (glowed) in wavelengths that NEAR’s X-ray/gamma-ray spectrometer (XGRS) was designed to measure.

Once analyzed, the data showed the elements magnesium, silicon and aluminum to be present. The abundance of these elements, and their distribution, suggests that Eros has not undergone the melting and chemical changes that larger, more differentiated bodies such as Earth have experienced.

As an S-class asteroid, Eros is very similar to chondritic meteorites chondrites, objects that formed directly from the solar nebula. Given that Eros has never undergone extreme heating, it is more or less the way it was when the solar system was young. Hence the use of the terms “primitive” and “Primordial” which are used to describe objects that formed in the early history of our solar system and retain their original composition to this day.

Prevailing theory suggests that chondritic bodies served as the building blocks for the planets we see today. Through a series of collisions smaller bodies formed larger bodies called planetesimals which in turn collided to form planets. As such, when we look at Eros, we are looking at one of type of building block from which our own planet was formed.

While these chemical composition findings do help pin an age on Eros, its overall physical structure is still not completely understood. Some asteroids are thought to be a collections of smaller bodies loosely bound together. This is apparently the case with asteroid Mathilde which NEAR visited on its way to Eros.

As NEAR gets closer to Eros, the XGRS instrument will be able to observe regions within specific craters. Having excavated material from within Eros, these craters allow a peek into the internal structure of the asteroid. If the interior is different than the surface, it is possible that this instrument may help determine how Eros is put together.

Related Links

° NEAR shows Eros is relic of solar system birth, Cornell University press release

° NEAR Shoemaker Observations Link Eros to Primordial Solar System, Johns Hopkins University press release

° NOAA/USAF Report of Solar-Geophysical Activity 3 May 2000

° NOAA/USAF Report of Solar-Geophysical Activity 4 May 2000

° NOAA/USAF Report of Solar-Geophysical Activity 5 May 2000

Background Information

° Focus On NEAR, SpaceRef

° NEAR gets Nearer to Eros, SpaceRef

° Asteroids and Comets, SpaceRef Directory

° Asteroid 433 Eros, SpaceRef Directory

° Asteroid 253 Mathilde, SpaceRef Directory

SpaceRef co-founder, Explorers Club Fellow, ex-NASA, Away Teams, Journalist, Space & Astrobiology, Lapsed climber.