There is something strange about the nearby asteroid 3200 Phaethon from Earth: it illuminates as it approaches the Sun, despite having no ice reserves that would normally cause this effect as they evaporate and disperse. sunlight.
They are ice-laden comets that become brighter as they heat up, not rocky asteroids, which is why Phaethon baffles astronomers for a long time. Now, a new study suggests that a particular chemical element might be behind this strange behavior.
“Phaeton is a curious object that is activated when it approaches the Sun,” says astronomer Joseph Masiero of the California Institute of Technology.
“We know it’s an asteroid and the source of the Geminids [meteor shower]. But it contains little or no ice, so we were intrigued by the possibility that sodium, which is relatively abundant in asteroids, could be the driving force behind this activity. “
Phaethon takes 524 days to complete a full orbit, during which time the Sun heats it up to a maximum of 1,050 Kelvin (777 degrees Celsius or 1,430 degrees Fahrenheit). Any asteroid ice would have burned long ago, but researchers used computer models to show that sodium could still be present, fading beneath the surface.
This warming and blowing could not only explain the illumination of the asteroid, as sodium escapes through cracks and fissures in the crust, but also from the ejection of rocks that can be seen from the Earth like the meteor shower of the Geminids every December. Phaethon’s weak gravitational pull would further facilitate debris removal.
We know that geminid meteors are relatively low in sodium due to the light they give off as they burn in the Earth’s atmosphere, and this can also be explained by the modeling done by the research team.
Experiments were then performed with fragments of the Allende meteorite, which landed in Mexico in 1969 and probably came from an asteroid like Phaethon. Upon heating, the behavior of the fragments confirmed that sodium could be converted to steam and released from an asteroid, at the kind of temperatures Phaethon probably experiences.
“This temperature is about the point where sodium escapes from its rocky components,” says planetary scientist Yang Liu of NASA’s Jet Propulsion Laboratory (JPL). “So we simulated this warming effect over a ‘day’ at Phaethon, its three-hour rotation period.”
“By comparing the minerals in the samples before and after our lab tests, sodium was lost while the other elements were left behind. This suggests that the same may happen at Phaethon and seems to agree with the results. of our models “.
In addition to offering some fascinating insights into what is happening at Phaethon, research also suggests that the distinction between rocky asteroids and icy comets may not be as clear as previously thought.
The results of modeling and experiments here could give astronomers some useful data that apply to other low-perihelion asteroids, which fly close to the Sun.
“Our latest discovery is that if conditions are right, sodium can explain the nature of some active asteroids, making the spectrum between asteroids and comets even more complex than we realized earlier,” says Masiero. .
The research has been published in Journal of Planetary Sciences.