6 September 2008
The first images from Rosetta’s OSIRIS imaging
system and VIRTIS infrared spectrometer were derived from raw data
this morning and have delivered spectacular results.
Steins
getting closer (actual animation)
"Steins looks like a diamond
in the sky," said Uwe Keller, Principal Investigator for the OSIRIS
imaging system from the Max Planck Institut Fuer
Sonnensystemforschung, Lindau.
Visible in the image are several small craters on the asteroid, and
two huge ones, one of which is 2 km in diameter, indicating that the
asteroid must be very old.
The images are 50 to 60 pixels in diameter, enough to characterise
the shape and other characteristics of the body of the asteroid.
Rita Schulz, Rosetta Project Scientist, said, "In the images is a
chain of impact craters, which must have formed from recurring
impact as the asteroid rotated. The impact may have been caused by a
meteoroid stream, or fragments from a shattered small body."
The chain is composed of about 7 craters. To determine the age of
the asteroid, a count of the craters on the asteroid’s surface has
been started (the more the number of craters, the older the
asteroid). So far, 23 craters have been spotted.
From the images, scientists will try and understand why the asteroid
is unusually bright, and how fine grains of the surface regolith
are. This will tell them more about how the asteroid formed.
Gerhard
Schwehm, Mission Manager for
Rosetta said, "It looks like a
typical asteroid, but it is
really fascinating how much we
can learn from just the images.
This is our first science
highlight; we certainly have a
lot of promising science ahead
of us. I’m already looking
forward to encountering our next
diamond in the sky, the much
bigger Lutetia."
The OSIRIS imaging system's Wide
Angle Camera (WAC) worked
perfectly through the fly-by.
The OSIRIS team expects that the
images that they will retrieve
from the Narrow Angle Camera
(NAC) will be of comparable
resolution. This will add to the
detailed colour information and
hence to knowledge of the
surface composition.
Science team members noted
that the Narrow Angle Camera (NAC) appears to have switched to safe
mode a few minutes before closest approach, but switched back on
after a few hours. The software is programmed to switch to safe mode
when certain parameter thresholds are crossed to protect the camera.
The team will concentrate investigating the reasons for this anomaly
once the science data has been analysed.
After analysis of the Rosetta data, Steins will be one of the
best-characterised asteroids so far.
Source: esa
