OSIRIS-REx is bringing more details of this space

rock to the forefront of science

steroids may not seem special at first
thought. There are so many of these
chunks of rock scattered throughout the
Solar System that one may not seem too
big a deal. But, like so many small bodies throughout
the universe, there is so much more than meets the
eye. These ancient remnants can tell astronomers
what the early Solar System was like when it was
formed around 4.6 billion years ago.
Asteroid 101955 Bennu was discovered on 11
September 1999 as part of the LINEAR Project,
a collaborative effort between NASA, the United
States Air Force and the Massachusetts Institute of
Technology’s (MIT) Lincoln Laboratory for tracking
near-Earth objects (NEOs). Bennu was one of many
objects to make this list as it makes its closest
approach to Earth every six years, coming roughly
within about 300,000 kilometres (186,000 miles)
from Earth, which is even closer than the Moon.
It makes one orbit around the Sun every 1.2 years,
making its orbit almost Earth-like.
In terms of size, Bennu would be considered huge
if it was to be placed on Earth. Having a diameter of
492 metres (1,614 feet), it is taller than the Empire

State Building in New York, United States, and the

Eiffel Tower in Paris, France. Its composition and

material are currently a mystery, however – as it is

such a small object in comparison to the planets

it’s hard to get any distinct visual observations on

it. NASA’s Spitzer Space Telescope managed to use

its infrared-spying abilities to provide a diameter

measurement, a low albedo reading and found the

thermal inertia (heat transfer) to vary with each

rotational period, which takes 4.3 hours. The analysis

of this data also revealed that the regolith grain

size is quite moderate, ranging from millimetres to

centimetres, and evenly distributed.

Based on spectroscopic analysis astronomers

have determined that Bennu is a B-type asteroid.

This is a rare type of carbonaceous asteroid that

could hold some exotic molecules formed over 4

billion years ago. The primitive composition of Bennu

could reveal organic molecules, volatiles and amino

acids that could have even brought life to Earth. Or,

looking even further back in time, did the materials

that led to our current Solar System stem from a

distant supernovae? These answers may have been

preserved in the frozen vacuum of space and haven’t

been tainted by the interference of our planet’s

atmosphere and environment before it could impact

Earth. It’s only by getting a sample of this unique,

nearby asteroid that these answers can be truly put

under the microscope, and that is exactly why NASA

has sent the Origins-Spectral Interpretation-Resource

Identification-Security-Regolith Explore, abbreviated

to OSIRIS-REx, spacecraft to investigate further.

Bennu

“ The primitive

composition of

Bennu could reveal

organic molecules”

Images of Bennu have been

given a 3D effect with the

help of red/blue glasses

A

Asteroid origins

It's believed Bennu was

formed at the same time as

the rest of the Solar System

some 4.6 billion years ago.

Peculiar shape

Bennu is shaped like a

spinning top – a shape that

astronomers are finding it

hard to account for.