{"id":13364,"date":"2019-02-01T00:02:14","date_gmt":"2019-01-31T16:02:14","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/osiris-rex-finds-rugged-terrain-on-asteroid-bennu\/"},"modified":"2019-02-01T00:02:14","modified_gmt":"2019-01-31T16:02:14","slug":"osiris-rex-finds-rugged-terrain-on-asteroid-bennu","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/osiris-rex-finds-rugged-terrain-on-asteroid-bennu\/","title":{"rendered":"OSIRIS-REx finds rugged terrain on asteroid Bennu"},"content":{"rendered":"
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NASA\u2019s OSIRIS-REx spacecraft\u2019s navigation camera captured this image of asteroid Bennu on Jan. 17 from a distance of approximately 1 mile (1.6 kilometers). The large boulder in partial shadow at the lower right of the frame is about 165 feet (50 meters) across. Credit: NASA\/Goddard\/University of Arizona\/Lockheed Martin<\/figcaption><\/figure>\n

Some time next year, NASA\u2019s OSIRIS-REx spacecraft will descend to the boulder-strewn surface of asteroid Bennu, reach out with a robotic arm, and fetch a sample for return to Earth, but an initial survey of the space rock millions of miles from Earth suggests the robotic mission may have few suitable targets for the touch-and-go maneuver.<\/p>\n

OSIRIS-REx is still in the early weeks of its stay at asteroid Bennu, a roughly 1,640-foot-wide (500-meter) object that oscillates inside and outside of Earth\u2019s orbit on each trip around the sun. Bennu\u2019s proximity to Earth, which makes it an impact risk to the planet in the distant future, allowed ground-based radars to scan the asteroid in detail, revealing its size and shape before OSIRIS-REx\u2019s launch in 2016.<\/p>\n

The radar observations made by stations at Arecibo, Puerto Rico, and Goldstone, California, did a \u201cphenomenal job of predicting the shape and topography of the asteroid for us,\u201d said Dante Lauretta, principal investigator for the $1 billion Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer mission at the University of Arizona, Tucson.<\/p>\n

On its approach to the asteroid last year, OSIRIS-REx showed Bennu is shaped like diamond, or a spinning top, just as the radar observations suggested.<\/p>\n

\u201cIt\u2019s really good news that we got it so right, and that all our mission design plans are valid as we move forward,\u201d Lauretta said Wednesday at a meeting of NASA\u2019s Small Bodies Assessment Group, a community of scientists with research interests in asteroids, comets and other small objects in the solar system.<\/p>\n

\u201cWe do have the expected, so-called \u2018spinning top\u2019 shape, which seems to be characteristic of a subset of the near-Earth asteroid population,\u201d Lauretta said.<\/p>\n

\u201cOne of the reasons we think it\u2019s top-shaped is because it\u2019s been accelerated by thermal pressures to sort of spin up,\u201d said Olivier Barnouin, a co-investigator on the OSIRIS-REx mission from the Johns Hopkins University Applied Physics Laboratory. \u201cYou can imagine if you take a top and start spinning up, if you have little rocks on it, things might go flying off.\u201d<\/p>\n

OSIRIS-REx\u2019s cameras searched for evidence of moons or debris around Bennu late last year.<\/p>\n

\u201cWe can confirm, to this point, that we have not identified any rocks that are flying around, and that there\u2019s no risk to the spacecraft, which actually I think is kind of remarkable because this place is very dynamic,\u201d Barnouin said in a Dec. 31 presentation of the mission\u2019s preliminary findings at Bennu.<\/p>\n

But Bennu did present some surprises to scientists, such as its jagged, craggy terrain covered with a collection of boulders, rock piles, craters and ridges.<\/p>\n

\u201cSome of the things that jump out at us right away from the asteroid\u2019s surface are the large boulders,\u201d Lauretta said Wednesday. \u201cWe are a looking at a pretty rough and rugged surface, more so than we expected.\u201d<\/p>\n

The first detailed images from OSIRIS-REx suggest Bennu exhibits the scars from collisions with other objects in the solar system, perhaps when Bennu orbited in the main asteroid belt between the orbits of Mars and Jupiter. The basins include up to a dozen large impact craters that measure up to 500 feet (150 meters) in diameter, according to Lauretta.<\/p>\n

\u201cWe\u2019re thinking that the asteroid surface\u2019s cratering age may be older than we expected, and may record its collisional history in the main asteroid belt,\u201d he said.<\/p>\n

Scientists believe the asteroid\u2019s visible surface may be between 100 million and 1 billion years old, and Lauretta says Bennu is likely a \u201crubble pile\u201d asteroid, made by the merging of several distinct objects. With the data already returned by OSIRIS-REx, scientists have calculated Bennu has a bulk density just 20 percent higher than that of water, and a bit less than that of Jupiter.<\/p>\n

Officials marked OSIRIS-REx\u2019s arrival at Bennu on Dec. 3, when the spacecraft flew over the asteroid\u2019s north pole. Subsequent passes over both poles and the equator allowed scientists to calculate the asteroid\u2019s mass, a crucial parameter for planning the probe\u2019s future trajectories.<\/p>\n

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An artist\u2019s concept of OSIRIS-REx at Bennu, with its sample collection arm extended. Credit: Lockheed Martin<\/figcaption><\/figure>\n

OSIRIS-REx is currently in the mission\u2019s \u201cOrbital A\u201d phase, following a maneuver Dec. 31 that directed the spacecraft into a slow-speed loop around Bennu that ranges between 1 mile and 1.3 miles (1.6 to 2.1 kilometers) from the asteroid. Due to Bennu\u2019s weak gravity field, thousands of times weaker than that of Earth, OSIRIS-REx travels at a speed of just one-tenth of a mile per hour, or 5 centimeters per second, relative to the asteroid.<\/p>\n

The orbital velocity of satellites circling the Earth can be as high as 17,500 mph (7.8 kilometers per second).<\/p>\n

OSIRIS-REx has set records, becoming the first mission to orbit an object as small as Bennu, and as the closest any spacecraft has orbited to any planetary body.<\/p>\n

The craft\u2019s navigation team on Earth is plotting the location of landmarks and other prominent features on the asteroid\u2019s surface. Beginning next month, OSIRIS-REx will fly on station-to-station trajectories around the asteroid, pulsing its thrusters to cover Bennu globally and periodically move to closer and farther distances.<\/p>\n

\u201cThe orbit phase is not really a science campaign phase,\u201d Lauretta said. \u201cIt\u2019s primarily there for the navigation team to transition from using star fields to landmarks on the asteroid surface. That transition is going very well, and are achieving navigation accuracies that are required for us to depart orbit in about four weeks and begin the detailed survey campaign of the mission.\u201d<\/p>\n

When the solar system formed more than 4.5 billion years ago, chunks of rock and ice collided as they circled the sun like the balls on a billiard table, eventually building up planets. The leftovers became asteroids and comets, and scientists believe Bennu still harbors the basic carbon-bearing organic molecules that were present in the early solar solar system, the stuff that may have helped seed life.<\/p>\n

The spacecraft carries three cameras \u2014 one for long-range viewing, a color camera for mapping, and another imager to take pictures as OSIRIS-REx collects samples from the asteroid\u2019s surface. The rest of OSIRIS-REx\u2019s suite of science instruments includes a thermal emission spectrometer to detect heat coming from the asteroid, a visible infrared spectrometer to locate minerals and organic materials, a laser altimeter provided by the Canadian Space Agency to create topographic maps, and a student-built X-ray spectrometer to identify individual chemical elements present on the asteroid.<\/p>\n

Data gathered by thermal emission and visible infrared spectrometer instruments \u2014 OTES and OVIRS \u2014 indicates clay minerals on the asteroid\u2019s surface contain hydroxyl molecules with oxygen and hydrogen molecules bonded together. This finding suggests Bennu\u2019s surface was once in contact with water, likely when the asteroid was part of a much larger parent body that was smashed to bits in a collision in the chaotic early solar system.<\/p>\n

One prominent feature of Bennu\u2019s landscape is a large boulder protruding from the surface near the south pole. While ground-based radar images suggested the boulder to be at least 33 feet, or 10 meters, in height, OSIRIS-REx imagery indicates is closer to 164 feet, or 50 meters, tall with a width of approximately 180 feet, or 55 meters, according to NASA.<\/p>\n

On approach to Bennu, ground controllers at Lockheed Martin in Denver \u2014 where OSIRIS-REx was built \u2014 unlatched the probe\u2019s robotic arm from its launch restraint for the first time. Over several days, the ground team commanded the arm to bend its joints and jettison a launch cover over the sample collection mechanism, which will release compressed air during a touch-and-go maneuver to force gravel and surface material into an on-board chamber for the journey back to Earth.<\/p>\n

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This mosaic image of asteroid Bennu is composed of 12 PolyCam images collected on Dec. 2 by the OSIRIS-REx spacecraft from a range of 15 miles (24 km). One of the darkest features on Bennu is visible at lower left. Credits: NASA\/Goddard\/University of Arizona<\/figcaption><\/figure>\n

One of the darkest features spotted so far on Bennu appears to be rich in magnetite and iron oxide, Lauretta said, based on early spectral measurements from OSIRIS-REx\u2019s instruments. Scientists are intrigued by the darker regions of the asteroid because they are expected to contain more carbon, the scientific pay dirt for the sample return mission.<\/p>\n

But officials will evaluate where OSIRIS-REx can safely reach the surface in the coming months, with the tough-and-go descent currently scheduled for July 4, 2020. That can be pushed back a few months, if necessary, before the spacecraft must depart Bennu in March 2021 to reach Earth in September 2023.<\/p>\n

\u201cThe OSIRIS-REx mission\u2019s sample site selection campaign starts next month, which is when we will start receiving science data at the resolution needed to make informed assessments about the safety of various regions on Bennu,\u201d Lauretta said in a written response Thursday to questions from Spaceflight Now.<\/p>\n

\u201cWe\u2019re thinking about sampling the surface \u2026 and the craters are starting to look as possibly good candidates because they\u2019re fairly smooth in structure, as far as we can tell at this point in the mission,\u201d Barnouin said.<\/p>\n

Email the author.<\/i><\/b><\/p>\n

Follow Stephen Clark on Twitter: @StephenClark1.<\/strong><\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

NASA\u2019s OSIRIS-REx spacecraft\u2019s navigation camera captured this image of asteroid Bennu on Jan. 17 from a distance of approximately 1 mile (1.6 kilometers). The large boulder in partial shadow at the lower right of the frame is about 165 feet (50 meters) across. Credit: NASA\/Goddard\/University of Arizona\/Lockheed Martin Some time next year, NASA\u2019s OSIRIS-REx spacecraft […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[1519,1526,472,2020,1527,1561,1563,2741],"class_list":["post-13364","post","type-post","status-publish","format-standard","hentry","category-news","tag-asteroids","tag-bennu","tag-lockheed-martin","tag-new-frontiers","tag-osiris-rex","tag-planetary-science","tag-solar-system","tag-university-of-arizona"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/13364"}],"collection":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/comments?post=13364"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/13364\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=13364"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=13364"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=13364"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}