Nasa researchers have spotted something weird on the surface of the dwarf planet
Ceres — a pair of mysterious shiny patches that reflect
The bright spots were imaged by the Dawn spacecraft, which is
whizzing through space on its way to Ceres, and should arrive in
orbit on 6 March. It’ll be the first spacecraft to study a
protoplanet at such close range.
“As we slowly approach the stage, our eyes transfixed on Ceres
and her planetary dance, we find she has beguiled us but left us
none the wiser,” said Chris Russell, principal investigator of the
Dawn mission. “We expected to be surprised; we did not expect to be
Two shiny patches have been spotted so far — the first from a distance of 83,000 kilometres and the second,
a dimmer companion, from 46,000 kilometres. Both are so far
too small to resolve properly with the camera.
Ceres is the largest object in the asteroid belt that lies
between the orbits of Mars and Jupiter, and was discovered in 1801.
It’s about 950 kilometres wide, and prior observation tells us that
it consists of a mix of rock and frozen water. It is suspected that
the latter might be the cause of the shiny patches.
Most of Ceres’ ice is hidden below the surface, but when it
bumps into other objects in the asteroid belt it could expose
patches of this type. That’s the working theory, anyway. Though
it’s countered by the fact that the shiny patches are only
reflecting about 40 percent of the light falling on them. Ice
should reflect nearly 100 percent. That’s being explained away as a
result of Dawn’s distance from the target.
Another option is that the bright spots are due to cryovolcanic
eruptions driven by radioactivity deep inside the
protoplanet, which spew ice, rather than lava, out onto the
surface. Water vapour measurements back this theory, but they could
also have come from ice.
A third possibility is that it’s not ice at all, but actually a
class of minerals called magnesium silicates that we’ve detected on
asteroids. We haven’t yet seen any evidence of this on Ceres,
making it the least likely possibility.
“We will have to wait for better resolution before we can make
such geologic interpretations,” said Russell, referring to the
distance from the protoplanet. The spacecraft will take photos as
it approaches, and then many more once it arrives in orbit and
properly orients itself to face the surface.
In short, this is one astronomical mystery that likely won’t go
unsolved for long.