Asteroid profile bennu
OSIRIS-REx is bringing more details of this space rock to the forefront of science
Catch up on the results from NASA spacecraft OSIRIS-REx
Asteroids 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.
“The primitive composition of Bennu could reveal organic molecules”