Featured Research

from universities, journals, and other organizations

NEAR Spacecraft Team Studies Small-Scale Features On Asteroid Eros

Date:
April 23, 2001
Source:
Johns Hopkins University Applied Physics Laboratory
Summary:
NEAR mission science team members have concluded that the majority of the small features that make up the surface of asteroid Eros more likely came from an unrelenting bombardment from space debris than internal processes.

NEAR mission science team members have concluded that the majority of the small features that make up the surface of asteroid Eros more likely came from an unrelenting bombardment from space debris than internal processes. Details of the research from NASA's Near Earth Asteroid Rendezvous (NEAR) mission were published this week in Science and are based on the NEAR Shoemaker spacecraft's Oct. 25-26, 2000, low-altitude flyover of asteroid Eros that brought the spacecraft to within about 3 miles of the surface of the asteroid.

Related Articles


"We think that impacts to the asteroid's surface have probably been the single-most dominant process in shaping the surface texture of the asteroid," says NEAR Project Scientist Dr. Andrew Cheng of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., which managed the mission for NASA. "We saw surface details such as regolith [surface dust and debris], craters and fields of small boulders in incredible detail. We also saw things that confound us, but we now have a more in-depth picture of Eros that will help us to decipher the asteroid's history."

During the flyover, simultaneous observations were taken by the spacecraft's multispectral imager and laser rangefinder over two tracks approximately 1 mile and 2.5 miles long that showed objects the size of a doghouse at three to four times better resolution than previously obtained. The data revealed an inordinate number of small boulders, a saturation of large craters and a dearth of small ones, crater "ponds," and unknown erosion processes.

A vast number of large craters, 1,630 to 3,280 feet (500 to 1,000 meters) in diameter, have been imaged, but there is a surprising scarcity of boulders large enough to make such impacts. There is more than 100 times the number of 10- to 12-foot (3- to 4-meter) boulders than there are impact craters in this region. Some angular or slab-like features were imaged that could indicate they are composed of stronger material than rounded objects. Some boulder clusters are thought to be fragments of a larger projectile that hit the asteroid.

The flyover also yielded evidence of an unusually low number of smaller craters. "There could be some unknown process, possibly something like seismic shaking following impacts, which is more likely on a small body such as Eros," says Dr. Joseph Veverka of Cornell University, Ithaca, N.Y., who heads the imaging team. "Other possibilities are processes that could erode or erase smaller craters such as micro-cratering [the pummeling of the surface by smaller objects] or thermal creep [the erosion of surface material through normal seasonal heating and cooling of the asteroid] that is eroding the smaller craters."

"We do know there is a substantial amount of regolith from erosion and impacts that is covering blocks [boulders] and craters possibly to a depth of several meters. So it could be that many smaller craters do exist but they're buried under the regolith," says Veverka. "A thick covering of fine dust that prevents us from seeing what lies beneath might also be part of the answer to why the asteroid has little color variation. It is possible that parts of Eros are covered in regolith as deep as a 10-story building."

The data also revealed ponds — flat surfaces at the bottom of craters — formed by regolith deposits. These ponds are intriguing science team members because of their extremely smooth surfaces. "The smoothness indicates that there is an efficient process on Eros which is able to sort out the finest component of the regolith from the coarser, more blocky portion and concentrate this fine material into some low-lying areas such as crater bottoms," Veverka says.

Moreover, the laser altimeter found that ponded deposits are not only smooth but also extremely horizontal — level relative to local gravity — as if formed by fluid-like motions. "It is astonishing that the total dry regolith of an asteroid like Eros can apparently be mobilized like a fluid," says Cheng. "There is no water on Eros, and there has not been any water, for billions of years. However, seismic shaking caused by impacts may be able to produce fluidized movement of regolith."

"Aprons" of debris at the base of some of the larger boulders indicate another phenomenon the researchers are studying: efficient erosion or disintegration of ejecta boulders (boulders forced out of a crater as the result of an impact) after they have landed on the surface. But scientists say they need to study higher resolution images to more definitively interpret the various forms of regolith that the low-altitude images have provided. "What causes this efficient disintegration remains a mystery," Veverka says. "But one we hope to solve over the coming months by studying the wealth of data that the NEAR mission has provided."

More information on the NEAR mission can be found at the NEAR mission Web site: http://near.jhuapl.edu.


Story Source:

The above story is based on materials provided by Johns Hopkins University Applied Physics Laboratory. Note: Materials may be edited for content and length.


Cite This Page:

Johns Hopkins University Applied Physics Laboratory. "NEAR Spacecraft Team Studies Small-Scale Features On Asteroid Eros." ScienceDaily. ScienceDaily, 23 April 2001. <www.sciencedaily.com/releases/2001/04/010423072910.htm>.
Johns Hopkins University Applied Physics Laboratory. (2001, April 23). NEAR Spacecraft Team Studies Small-Scale Features On Asteroid Eros. ScienceDaily. Retrieved December 22, 2014 from www.sciencedaily.com/releases/2001/04/010423072910.htm
Johns Hopkins University Applied Physics Laboratory. "NEAR Spacecraft Team Studies Small-Scale Features On Asteroid Eros." ScienceDaily. www.sciencedaily.com/releases/2001/04/010423072910.htm (accessed December 22, 2014).

Share This


More From ScienceDaily



More Space & Time News

Monday, December 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

NASA Prepares for Next Phase of Hubble Successor

NASA Prepares for Next Phase of Hubble Successor

Reuters - Innovations Video Online (Dec. 22, 2014) Scientists and engineers prepare for the next phase of the James Webb Space Telescope, the scientific successor to the Hubble. Nathan Frandino reports. Video provided by Reuters
Powered by NewsLook.com
Spokesman: 'NORAD Ready to Track Santa'

Spokesman: 'NORAD Ready to Track Santa'

AP (Dec. 19, 2014) Pentagon spokesman Rear Adm. John Kirby said that NORAD is ready to track Santa Claus as he delivers gifts next week. Speaking tongue-in-cheek, he said if Santa drops anything off his sleigh, "we've got destroyers out there to pick them up." (Dec. 19) Video provided by AP
Powered by NewsLook.com
NASA's Planet-Finding Kepler Mission Isn't Over After All

NASA's Planet-Finding Kepler Mission Isn't Over After All

Newsy (Dec. 18, 2014) More than a year after NASA declared the Kepler spacecraft broken beyond repair, scientists have figured out how to continue getting useful data. Video provided by Newsy
Powered by NewsLook.com
Rover Finds More Clues About Possible Life On Mars

Rover Finds More Clues About Possible Life On Mars

Newsy (Dec. 17, 2014) NASA's Curiosity rover detected methane on Mars and organic compounds on the surface, but it doesn't quite prove there was life ... yet. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins