Asteroid Robotic News
May 25, 2012 13:25:0
NASA Scientist Figures Way to Weigh Space Rock
By Source: NASA

PASADENA -  A scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., has accurately determined the mass of a nearby asteroid from millions of miles away. The celestial equivalent of "guess your weight" was achieved by Steve Chesley of JPL's Near-Earth Object Program Office by utilizing data from three NASA assets - the Goldstone Solar System Radar in the California desert, the orbiting Spitzer Space telescope, and the NASA-sponsored Arecibo Observatory in Puerto Rico.

Chesley presented his findings this past Saturday, May 19, at the Asteroids, Comets and Meteors 2012 meeting in Niigata, Japan.

For Chesley to define the asteroid's mass, he first needed to understand its orbit and everything that could affect that orbit -- including neighboring celestial bodies and any propulsive force (however minute) the asteroid could generate.

Incorporating extraordinarily precise observations collected by astronomer Michael Nolan at Arecibo Observatory in September 2011, Arecibo and Goldstone radar observations made in 1999 and 2005, and the gravitational effects of the sun, moon, planets and other asteroids, Chesley was able to calculate how far the asteroid deviated from its anticipated orbit. He found that 1999 RQ36 had deviated from the mathematical model by about 100 miles (160 kilometers)in the past 12 years.  The only logical explanation for this orbital change was that the space rock itself was generating a minute propulsive force known in space rock circles as the Yarkovsky effect.

The Yarkovsky effect is named for the 19th-century Russian engineer who first proposed the idea that a small, rocky space object would, over long periods of time, be noticeably nudged in its orbit by the slight push created when it absorbs sunlight and then re-emits that energy as heat. The effect is hard to measure because it's so infinitesimally small.

"At its peak, when the asteroid is nearest the sun, the Yarkovsky force on 1999 RQ36 is only about a half ounce -- around the weight of three grapes," said Chesley.  "When you're talking about the force of three grapes pushing something with a mass of millions of tons, it takes a lot of high-precision measurements over a long time to see any orbital changes. Fortunately, the Arecibo Observatory provided a dozen years of great radar data, and we were able to see it."

The final piece to the puzzle was provided by Josh Emery of the University of Tennessee, Knoxville, who used NASA's Spitzer Space Telescope in 2007 to study the space rock's thermal characteristics. Emery's measurements of the infrared emissions from 1999 RQ36 allowed him to derive the object's temperatures. From there he was able to determine the degree to which the asteroid is covered by an insulating blanket of fine material, which is a key factor for the Yarkovsky effect.

With the asteroid's orbit, size, thermal properties and propulsive force (Yarkovsky effect) understood, Chesley was able to perform the space rock scientist equivalent of solving for "X" and calculate its bulk density.

"While 1999 RQ36 weighs in at about 60 million metric tons, it is about a half kilometer across," said Chesley. "That means it has about the same density as water, so it's more than likely a very porous jumble of rocks and dust."
Asteroid 1999 RQ36 is of particular interest to NASA as it is the target of the agency's OSIRIS-REx  (Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer) mission. Scheduled for launch in 2016, ORIRIS-Rex will visit 1999 RQ36, collect samples from the asteroid and return them to Earth.

 
 This computer generated image of asteroid 1999 RQ36 was derived from data acquired by the NASA-supported Arecibo Observatory in Puerto Rico. Image credit: NASA/NSF/Cornell/Nolan

NASA detects, tracks and characterizes asteroids and comets passing relatively close to Earth using both ground- and space-based telescopes. The Near-Earth Object Observations Program, commonly called "Spaceguard," discovers these objects, characterizes a subset of them, and establishes their orbits to determine if any could be potentially hazardous to our planet. JPL manages the Near-Earth Object Program Office for NASA's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena. JPL also manages the Spitzer Space Telescope and Goldstone Solar System Radar.

 

More Interactive Photography
Gale Crator InterActive First look crisp look around Gale Crator This 360-degree, full-resolution panorama from NASA's Curiosity rover shows the area all around...
Endeavour nose gear in OPF InterActive Endeavour nose gear in OPF This was shot from forward and underneath Space Shuttle Endeavour in the Orbiter Processing...
Endeavor engine compartment InterActive Endeavor engine compartment View into the Space Shuttle's engine compartment with the three main engines removed.
Endeavor engine compartment InterActive Endeavor engine compartment View into the Space Shuttle's engine compartment with the three main engines removed.
Endeavour Cargo Bay InterActive Endeavour Cargo Bay This image was shot from the forward end of Space Shuttle Endeavour's cargo ba as it sits in...
Interior view of the Space Shuttle Endeavour forward flight deck. InterActive Interior view of the Space Shuttle Endeavour forward flight deck. Interior view of the Space Shuttle Endeavour aft flight deck.
Endeavour Forward Flight Deck InterActive Endeavour Forward Flight Deck Interior view of the Space Shuttle Endeavour forward flight deck.
Atlas V with Mars Science Laboratory payload InterActive Atlas V with Mars Science Laboratory payload The rover Curiosity will carry the biggest, most advanced suite of instruments for scientific...
Curiosity rover InterActive Curiosity rover NASA's Mars Science Laboratory Curiosity rover, a mobile robot for investigating Mars' past or...
Curiosity rover InterActive Curiosity rover NASA's Mars Science Laboratory Curiosity rover, a mobile robot for investigating Mars' past or...
Gravity Recovery and Interior Laboratory InterActive GRAIL The Gravity Recovery and Interior Laboratory mission's primary science objectives will be to...
Atlas V AV-029 InterActive Atlas V AV-029 ULA Atlas V number AV-029 reaches launch pad on August 4th, 2011. In less than 1 day this Atlas...
Atlas V up close InterActive Atlas V up close Get to know the Atlas V up close. Explore the rivets in this 74.62 megapixel image of the Atlas...
JUNO Atlas V InterActive JUNO Atlas V ULA Atlas V with the JUNO probe sitting atop at Cape Canaveral Air Force Station is ready for...
Atlantis at wheels stop on runway 15 InterActive Atlantis on runway Space Shuttle Atlantis returned to Earth in the predawn hours of July 21st, 2011. Marking the...
Atlantis at wheels stop on runway 15 InterActive Atlantis at wheels stop on runway 15 Space Shuttle Atlantis returned to Earth in the predawn hours of July 21st, 2011. Marking the...
Atlantis and tower InterActive Atlantis and tower Space shuttle Atlantis waits to receive payload for the final space shuttle mission STS-135,...
Atlantis payload preparations InterActive Atlantis payload preparations Space shuttle Atlantis at pad 39A. The payload canister can be seen lifted in to position to...
Walk with the astronauts InterActive Walk with the astronauts A view of the 195ft level of the fixed service structure. This where the astronauts arrive at...
Last Space Shuttle prepares for launch InterActive Last Space Shuttle prepares for launch A close in look at space shuttle Atlantis on June 17th. Launch preparations are on going for...
The last space shuttle to be on the launch pad InterActive The last space shuttle to be on the launch pad Space shuttle Atlantis, the last space shuttle to flight begins launch prepartions at pad 39A...
Last space shuttle arrives at launch pad InterActive Last space shuttle arrives at launch pad Space shuttle Atlantis is seen here from the top of the rotating service structure the moring...
The last space shuttle has left the building InterActive The last space shuttle has left the building Space shuttle Atlantis rolls out of the Vehicle Assembly Building for the last time on the...
Space Shuttle Atlantis prepared to rollout to pad   InterActive Space Shuttle Atlantis prepared to rollout to pad Space shuttle Atlantis complete with the solid rocket boosters and external tank that will...
HiRes Atlantis hanging in VAB InterActive HiRes Atlantis hanging in VAB HiRes image of Space Shuttle Atlantis hanging in the Vehical Assembly Building. This shot was...
Atlantis vertical from VAB Level 5 InterActive Atlantis vertical from VAB Level 5 Space Shuttle Atlantis after being lifted into the verticle position before being mated to the...
Atlantis vertical InterActive Atlantis vertical Space Shuttle Atlantis hangs vertical before removing the rear hoist and lifting it for the...
Atlantis rolling vertical InterActive Atlantis rolling vertical Here Space Shuttle Atlantis is almost vertical being positioned to soon be mated to the...
Atlantis hanging in VAB InterActive Atlantis hanging in VAB Space Shuttle Atlantis is seen here hanging about 10 feet above the VAB floor. It has justed...
Endeavour at night InterActive Endeavour at night Space shuttle Endeavour seen here at night as launch preparation continue for the first launch...
Atlantis rolling over to VAB for final mission InterActive Atlantis rolling over to VAB for final mission Space Shuttle Atlantis rolling over the VAB for the last time. Atlantis is scheduled to be the...
Atlantis outside VAB for employee photos InterActive Atlantis outside VAB for employee photos Space shuttle Atlantis, the last space shuttle, pauses during rollover from the OPF to the VAB...
Hi Resolution image of the last space shuttle InterActive Hi Resolution image of the last space shuttle Hi Resolution composit image of the last space shuttle, Atlantis, as it sits atop the transport...
Atlantis in the VAB InterActive Atlantis in the VAB Nice 360 degree view of the VAB with Atlantis being preped for the Lift and Mate procedure
Atlantis on the sled in VAB InterActive Atlantis on the sled in VAB Explore the VAB with Space Shuttle Atlantis on the sled after rollover to the VAB jst before...
Atlantis being attached to sling InterActive Atlantis being attached to sling Full 360 degree panorama from inside the VAB as Space Shuttle Atlantis is attached to the sling...
Endeavour after RSS retraction InterActive Endeavour after RSS retraction Hi-Res image of Space Shuttle Endeavour on the launch pad 39A minutes after the RSS was...
The Mound STS-134 4/29 Attempt InterActive The Mound STS-134 4/29 Attempt This a 360 degree panorama from the mound of the KSC media center. This was the scence about an...
Alpha Magnetic Spectrometer (AMS) InterActive Alpha Magnetic Spectrometer (AMS) The Alpha Magnetic Spectrometer-2, a particle physics detector designed to search for various...
AMS in the SSPF InterActive AMS in the SSPF The Alpha Magnetic Spectrometer-2, a particle physics detector designed to search for various...
Here is Space Shuttle Endeavour just after sunrise InterActive Here is Space Shuttle Endeavour just after sunrise Here is Space Shuttle Endeavour just after sunrise the morning it arrived from the VAB. How...
Endeavour in the VAB InterActive Endeavour in the VAB Space Shuttle Endeavour sitting stacked and ready atop the crawler to rollout the launch pad.
Endeavour in the VAB InterActive Endeavour in the VAB Space Shuttle Endeavour sitting stacked and ready atop the crawler to rollout the launch pad.
Space Shuttle Discovery final towover InterActive Space Shuttle Discovery final towover View of Space Shuttle Discovery 4 hours after returning to Earth for the last time. Discovery...
Space Shuttle Discovery Final Launch InterActive Space Shuttle Discovery Final Launch This a 360 degree panorama taken 3 mile from the launch pad capturing the final lift off of...
Space shuttle Discovery final launch InterActive Space shuttle Discovery final launch This a 360 degree panorama taken 3 mile from the launch pad capturing the final lift off of...
Discovery at Night InterActive Discovery at Night This a panorama of Space Shuttle Discovery shortly after RSS retraction on 11/3/2010 preparing...
GRIP DC-8 Panorama InterActive GRIP DC-8 Panorama Interior of forward section of NASA GRIP aircraft while configured for studding hurricane...
GRIP DC-8 Interior InterActive GRIP DC-8 Interior Interior of forward section of NASA GRIP aircraft while configured for studding hurricane...
NASA GRIP DC-8 InterActive NASA GRIP DC-8 The NASA DC-8 is a four-engine jet transport that has been highly modified to support the...
Endeavour on pad InterActive Endeavour ready for launch HiRes image of Endeavour at Pad 39A
AMS-2 Antimatter Telescope InterActive AMS-2 Antimatter Telescope Explore the SSPF and ESA's Antimatter Telescope. 360 rotating,zoomable Panorama!
Spectacular ultra hi-rez interactive shot of the Space Shuttle Endeavour on the launch pad for the last time InterActive Explore LC-39A !! Spectacular ultra hi-rez interactive shot of the Space Shuttle Endeavour on the launch pad for...