En route to the asteroid Bennu, NASA’s OSIRIS-REx space probe captured this image of Jupiter and three of its moons. It make look plain vanilla, but consider that the spacecraft was 76 million miles (122 million km) from Earth and 418 million miles (673 million km) from Jupiter on Feb. 12, when the photo was taken. I like it because the view reminds me of how Jupiter looks like through a small telescope with its two dark “stripes” or equatorial cloud belts and star-like moons. PolyCam is OSIRIS-REx’s longest range camera, capable of capturing images of the asteroid Bennu from a distance of 1.2 million miles (2 million km)..
OSIRIS-REx, short for Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer, is outbound to the dark, carbon-rich asteroid Bennu. The trip’s a long one — the probe won’t arrive until 2018 — and includes an Earth flyby in September to pick up additional speed. Besides mapping and studying the asteroid’s surface, the mission highlight will be to gather a sample of at least 60 grams (2.1 ounces) of Bennu’s soil and return it to Earth for analysis in 2023.
From observations of the asteroid made from Earth, we know that Bennu is made of very ancient and pristine material little changed since the asteroid first formed more than 4.5 billion years ago. Rich in carbon, scientists hope the sample will help us learn more about the source of the organic (carbon-containing) compounds that led to the formation of life on Earth.
Bennu’s roughly spherical in shape despite its small size of about 1,614 ft or 0.306 mile across and listed as a potentially hazardous asteroid (PHA). Based on our knowledge of its orbit, there’s a 1 in 2,700 chance of it impacting Earth in the late 22nd century. Yes, all the more reason to study it up close.
Besides taking snaps of Jupiter to test its cameras, OSIRIS-REx has also been looking for asteroids that share Earth’s orbit called Trojans. Trojans around other planets pile into stable “gravity wells” called Lagrange points, which lie in the planet’s orbit but precede or follow it. Jupiter for instance has two huge families of Trojan asteroids orbiting 60° ahead and 60° behind the giant planet. They number in the many thousands!
OSIRIS-REx is currently traveling through Earth’s fourth Lagrange point, which is located 60° ahead in Earth’s orbit around the sun, about 90 million miles (150 million km) from our planet. The mission team is using the opportunity to photograph the area with the spacecraft’s MapCam camera in the hope of identifying Earth-Trojan asteroids in the region.
Although scientists have discovered thousands of Trojan asteroids accompanying other planets, only one Earth-Trojan has been identified to date, asteroid 2010 TK7. Scientists predict that there should be more Trojans sharing Earth’s orbit, but they are difficult to detect from Earth as they appear near the sun on the Earth’s horizon.
“Because the Earth’s fourth Lagrange point is relatively stable, it is possible that remnants of the material that built Earth are trapped within it,” said Dante Lauretta, principal investigator for the mission. “So this search gives us a unique opportunity to explore the primordial building blocks of Earth.”
Curiosity is one of the best things about being human. We’ll never stop trying to find the thread that connects the present to our origins in stardust — the quest makes me proud to be a citizen of the universe. Someone’s got to uncover the full story and tell it, right?