Bennu catch-up
Bennu’s welcoming shot
After a two-year, 2.2-million-kilometre (1.4-million-mile) journey, OSIRIS-REx was finally
making its highly anticipated approach to Bennu. On 2 December 2018, on its approach,
the spacecraft put its 20-centimetre (eight-inch) PolyCam to work in photographing
Bennu in fantastic detail. The result was a beautiful mosaic image consisting of 12 images
taken from just 24 kilometres (15 miles) away.
Using the same images astronomers were also able to construct a 3D model of the
asteroid, demonstrating features as small as six metres (20 feet). The observations and
model confirmed many aspects about the then-mysterious ball of rock that astronomers
predicted, such as its shape, diameter, rotation speed and inclination. The only outlier
was a large boulder near the south pole of the asteroid. The ground-based model
suggested the boulder would be 10 metres (33 feet) in height, but up-close observations
showed it to be closer to 50-metres (164-feet) high, with a width of approximately 55
metres (180 feet).Another source of water found
OSIRIS-REx is already making fascinating discoveries about Bennu – and it hasn’t even collected
a sample yet! The first major discovery from this mission was made by two of its instruments,
the OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) and the OSIRIS-REx Thermal Emission
Spectrometer (OTES). These instruments revealed the presence of water inside the clays that
make up the asteroid. These ‘hydroxyls’, which are molecules containing hydrogen and oxygen,
exist over the entire asteroid and could hold important clues about the origins of Earth’s water.
“The presence of hydrated minerals across the asteroid confirms that Bennu, a remnant from
early in the formation of the Solar System, is an excellent specimen for the OSIRIS-REx mission
to study the composition of primitive volatiles and organics,” says Amy Simon, OVIRS deputy
instrument scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, United
States. “When samples of this material are returned by the mission to Earth in 2023, scientists will
receive a treasure trove of new information about the history and evolution of our Solar System.”
Mapping the entire asteroid is just
one of the main scientific goalsOSIRIS-REx will contact Bennu
withthe Touch-And-Go Sample
ArmMechanism,orTAGSAMThis 3D model of Bennu has revealed
a terrain that exhibits both clusters of
boulders and smooth regionsImproving asteroid tracking
with OSIRIS-REx
When OSIRIS-REx made its approach in early
December 2018, this began a near two-year, close-up
adventure to find out what this intriguing asteroid has
to offer. On its approach NASA compiled a manifesto
to explain the importance of the OSIRIS-REx mission.
It aim to understand the forces that move asteroids,
help in detecting hazardous objects and improve
predictions of any potential collisions.
As Bennu is about half a kilometre (a third of a mile)
wide, Bennu is large enough to potentially reach the
surface of the Earth and cause widespread damage.
These observations will keep track of the asteroid’s
location to within a few kilometres.
Scientists have found it hard to estimate its
future trajectory around the Sun due to the
gravitational interference of Earth, the Sun and
other objects. This is why predictions for Bennu’s
trajectory get fuzzy around 2060. “There are a lot
of factors that might affect the predictability of
Bennu's trajectory in the future, but most of them
are relatively small,” says William Bottke, an asteroid
expert at the Southwest Research Institute in Boulder,
Colorado, United States, and a participating scientist
on the OSIRIS-REx mission. "The one that's most
sizeable is Yarkovsky.”
These are just a few benefits of asteroid examination
that will benefit our understanding of asteroids in a
scientific sense and in a tracking sense.“Scientists will receive a treasure
trove of new information about
the history and evolution of our
Solar System”
Asteroid profile