NASAThe first mission to return a sample from an ancient asteroid arrived at its target, Asteroid Bennu, on December 3, 2018. This mission, Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer, or OSIRIS-REx, is a seven-year journey set to end with the delivery to Earth of at least 2.1 ounces (60 grams) and possibly up to nearly four and a half pounds (two kilograms) of sample. It promises to be the largest amount of extraterrestrial material brought back from space since the Apollo era.
The twentieth anniversary of the asteroid’s discovery was in September 2019, and scientists have been collecting data ever since. Here’s what we already know (and some of what we hope to discover) about this pristine remnant from the early days of our solar system.
1. It’s very, very dark …
Bennu is classified as a type B asteroid, which means it contains a lot of carbon in and along with its various minerals. Bennu’s carbon content creates a surface on the asteroid that reflects about four percent of the light that hits it – and that’s not much. By contrast, the brightest planet in the solar system, Venus, reflects about 65% of the incoming sunlight, and the Earth reflects about 30%. Bennu is a carbonaceous asteroid that has not undergone drastic changes that alter its composition, which means that above and below its surface deeper than pitch black have been chemicals and rocks since the birth of the solar system.
2. … And very, very old.
Bennu has been (mostly) undisturbed for billions of years. Not only is it conveniently close and carbonaceous, it’s also so primitive that scientists have calculated that it formed in the first 10 million years of our solar system’s history – over 4.5 billion years ago. Thanks to the Yarkovsky effect – the slight push created when the asteroid absorbs sunlight and re-emits that energy in the form of heat – and gravitational tugs from other celestial bodies, it has moved closer and closer to Earth from its probable location. birth: the main asteroid belt between Mars is Jupiter.
3. Bennu is a “pile of rubble” asteroid, but don’t let the name fool you.
Is Bennu space junk or a scientific treasure? While “pile of rubble” sounds like an insult, it’s actually a true classification of astronomy. Rubble heap asteroids like Bennu are celestial bodies made up of many pieces of rocky debris that gravity has compressed together. This type of debris is produced when an impact shatters a much larger body (for Bennu, it was a parent asteroid about 60 miles away. [about 100 km] wide). Bennu, by contrast, is about as tall as the Empire State Building. It probably only took a few weeks for these fragments of space debris to merge into the pile of rubble that is Bennu. Bennu is full of holes inside, with 20-40 percent of its volume being empty space. The asteroid is actually in danger of flying away if it starts spinning much faster or interacts too closely with a planetary body.
4. Asteroids can provide hints about the origin of all life on Earth …
Bennu is a primordial artifact preserved in the vacuum of space, in orbit between planets and moons, asteroids and comets. Because it is so ancient, Bennu could be made of material containing molecules that were present when life first formed on Earth. All life forms on Earth are based on chains of carbon atoms linked with oxygen, hydrogen, nitrogen and other elements. However, organic material like the kind scientists hope to find in a Bennu sample doesn’t necessarily come from biology. It would, however, be further research by scientists to discover the role played by organically rich asteroids in catalyzing life on Earth.
5.… but also platinum and gold!
Extraterrestrial jewelry looks fantastic, and Bennu is likely rich in platinum and gold compared to the average crust on Earth. While most are not made almost entirely of solid metal (but asteroid 16 Psyche might be!), Many asteroids contain elements that could be used industrially in place of Earth’s limited resources. Studying this asteroid closely will answer questions about the feasibility of asteroid mining during exploration and travel in deep space. Although rare metals attract the most attention, water is likely to be Bennu’s most important resource. Water (two hydrogen atoms bonded to one oxygen atom) can be used for drinking or separated into its components to obtain breathable air and rocket fuel. Given the high cost of transporting material into space, if astronauts can extract water from an asteroid for life support and fuel, the cosmic afterlife is closer than ever to accessible humans.
6. Sunlight can change the entire trajectory of the asteroid.
Gravity isn’t the only factor involved in Bennu’s fate. The side of Bennu facing the Sun is heated by sunlight, but a day on Bennu lasts only 4 hours and 17.8 minutes, so the part of the surface facing the Sun changes constantly. As Bennu continues to rotate, it expels this heat, which gives the asteroid a small push toward the Sun of about 0.18 miles (about 0.29 kilometers) per year, changing its orbit.
7. There is a small chance that Bennu will have an impact on Earth towards the end of the next century.
The NASA-funded Lincoln Near-Earth Asteroid Research Team discovered Bennu in 1999. NASA’s Office of Planetary Defense Coordination continues to monitor near-Earth (NEO) objects, particularly those like Bennu that they will find approximately 4.6 million miles (7.5 million kilometers) from Earth’s orbit and are classified as potentially dangerous objects. Between the years 2175 and 2199, the chance of Bennu impacting Earth is only 1 in 2,700, but scientists still don’t want to turn their backs on the asteroid. Bennu swoops through the solar system on a path that scientists have confidently predicted, but will refine their predictions with OSIRIS-REx’s measurement of the Yarkovsky effect and future observations by astronomers.
8. Sampling Bennu will be harder than we thought.
Early Earth observations of the asteroid suggested it had a smooth surface with a regolith (the top layer of loose, unconsolidated material) made up of particles smaller than an inch (a couple of centimeters) in size – at most. As the OSIRIS-REx probe was able to take pictures at higher resolution, it became apparent that Bennu sampling would be far more dangerous than previously believed: new images of Bennu’s surface show that it is for the more covered with massive boulders, not small rocks. OSIRIS-REx was designed to be navigated within an area on Bennu of nearly 2,000 square yards (meters), roughly the size of a car park with 100 spaces. Now, he must maneuver to a safe spot on Bennu’s rocky surface within a limit of less than 100 square meters, an area of about five parking spaces.
9. Bennu is named after an ancient Egyptian deity.
Bennu was named in 2013 by a nine-year-old from North Carolina who won the Name that asteroid! competition, a collaboration between the mission, the Planetary Society and the LINEAR asteroid survey that Bennu discovered. Michael Puzio won the competition by suggesting that the spacecraft’s TAGSAM (Touch-and-Go Sample Mechanism) arm and solar panels resemble the neck and wings in Bennu’s illustrations, which ancient Egyptians usually depicted as a gray heron. Bennu is the ancient Egyptian deity linked to the Sun, creation and rebirth – Puzio also noted that Bennu is the living symbol of Osiris. The myth of Bennu fits the asteroid itself, as it is a primitive object dating back to the creation of the Solar System. The themes of origins and rebirth are part of the history of this asteroid. Birds and bird-like creatures are also symbols of rebirth, creation, and origins in various ancient myths.
10. Bennu is still surprising us!
The ship’s navigation camera observed that Bennu was throwing up streams of particles a couple of times a week. Bennu is apparently not just a rare active asteroid (only a handful of them have yet been identified), but perhaps with Ceres explored by NASA’s Dawn mission, among the first of its kind that humanity has observed from a spacecraft. More recently, the mission team discovered that sunlight can break rocks on Bennu and that it has pieces of another asteroid scattered across its surface. As the mission progresses, more pieces will be added to Bennu’s cosmic puzzle, each bringing the evolutionary story of the solar system into ever-sharper ways.
Goddard provides general mission management, systems engineering and security and mission assurance for OSIRIS-REx. Dante Lauretta of the University of Arizona, Tucson, is the principal investigator, and the University of Arizona also leads the science team and the scientific observation planning and data processing of the mission. Lockheed Martin Space of Denver built the spacecraft and is providing flight operations. Goddard and KinetX Aerospace are responsible for navigating the OSIRIS-REx spacecraft. OSIRIS-REx is the third mission of NASA’s New Frontiers Program, which is managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington.