In the last December, scientists discovered an active asteroid labeled 6478 Gault, inside the asteroid belt. They found that the asteroid leaving two trails of dust in its wake — active behavior that is associated with comets but rarely seen in asteroids.
While astronomers are as yet thinking about the reason for Gault’s comet-like action, an MIT-drove group recently reports that it has caught the space rock in the act of changing color, from red to blue. It is the first time through scientists have observed a color-shifting asteroid, continuously.
Scientists also affirmed that the asteroid is rocky- evidence that the asteroid’s tail, though seemingly comet-like, is caused by an entirely different mechanism, as comets are not rocky but more like loose snowballs of ice and dust.
Michael Marsset, a postdoc in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS) said, “That was a huge surprise. We think we have witnessed the asteroid losing its reddish dust to space, and we see the asteroid’s underlying fresh blue layers.”
“It’s the first time to my knowledge that we see a rocky body emitting dust, a little bit like a comet. It means that probably some mechanism responsible for dust emission is different from comets and different from most other active main-belt asteroids.”
In March, Scientists started their exploration for Gault’s activity, when they secured observation time at NASA’s Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. For more than two nights, they observed the asteroid. Then by using high-precision spectrograph, they classified asteroid’s incoming light into various frequencies, or colors, the relative intensities of which can give scientists an idea of an object’s composition.
Based on their analysis, they determined that the asteroid’s surface is composed mainly of silicate, a dry, rocky material, similar to most other asteroids, and, more importantly, not at all like most comets.
During their observation, scientists discovered that the rock was changing color in the near-infrared, from red to blue.
EAPS Research Scientist Francesca DeMeo said, “We’ve never seen such a dramatic change like this over such a short period of time.”
Scientists noted, “They are likely seeing the asteroid’s surface dust, turned red over millions of years of exposure to the sun, being ejected into space, revealing a fresh, less irradiated surface beneath, that appears blue at near-infrared wavelengths.”
“Interestingly, you only need a very thin layer to be removed to see a change in the spectrum. It could be as thin as a single layer of grains just microns deep.”
What causing the asteroid to turn color?
According to scientists, the reason for the color shift, and the asteroid’s comet-like activity is likely due to the same mechanism: a fast spin. Scientists suggest that the asteroid may be spinning fast enough to whip off layers of dust from its surface, through sheer centrifugal force.
Marsset said, “About 10 percent of asteroids spin very fast, meaning with a two- to three-hour rotation period, and it’s most likely due to the sun spinning them up.”
Scientists are now further planning to study the asteroid for further clues to activity when it next becomes visible in the sky.
DeMeo said, “I think [the group’s study] reinforces the fact that the asteroid belt is a dynamic place. While the asteroid fields you see in the movies, all crashing into each other is an exaggeration, there is a lot happening out there every moment.”
This research, published in the journal Astrophysical Journal Letters- was funded, in part, by the NASA Planetary Astronomy Program.