Featured Research

from universities, journals, and other organizations

Near Spacecraft Reveals Major Features Of Eros Asteroid

Date:
February 9, 1999
Source:
Johns Hopkins University Applied Physics Laboratory
Summary:
Asteroid 433 Eros is slightly smaller than predicted, with at least two medium-sized craters, a long surface ridge, and a density comparable to the Earth's crust, according to measurements from NASA's Near Earth Asteroid Rendezvous (NEAR) spacecraft.

Asteroid 433 Eros is slightly smaller than predicted, with at least two medium-sized craters, a long surface ridge, and a density comparable to the Earth's crust, according to measurements from NASA's Near Earth Asteroid Rendezvous (NEAR) spacecraft.

NEAR's science instruments observed about two-thirds of Eros on Dec. 23, 1998, as the spacecraft flew by the asteroid following an unsuccessful firing of its main engine a few days earlier. A subsequent successful firing of the engine put NEAR on course to rendezvous with Eros to begin its planned yearlong orbital mission starting in mid-February 2000.

Scientists and engineers at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, MD, which manages the mission, and science team members from affiliated institutions quickly planned the valuable flyby observations in the wake of the unsuccessful engine burn on Dec. 20.

During the flyby, 222 photos and supporting spectral observations were taken from as close as 2,375 miles (3,830 kilometers) from the asteroid by the spacecraft's multispectral imager, infrared spectrometer, and radio science experiment. "The flyby of Eros has given us fundamental information that will help us plan a better orbital mission at Eros," said Dr. Andrew F. Cheng, NEAR project scientist at APL. "It has taken some of the risk out of our orbit insertion maneuver and early operations."

First observed from the Earth more than 100 years ago, Eros was known to be an S-type asteroid with high concentrations of silicate minerals and metal. However, few details about its structure or composition are observable from the ground. The NEAR flyby produced evidence of variations in surface color and reflected light (or albedo) that suggest the asteroid has a diverse surface makeup. Closer observations during the comprehensive yearlong orbital study of Eros will be needed to determine its precise composition.

The science team has determined that Eros is slightly smaller than originally estimated from ground-based radar observations, with a size of 21 by 8 by 8 miles (33 by 13 by 13 kilometers), versus an estimate of 25.3 by 9 by 8 miles (40.5 by 14.5 by 14 km). The asteroid rotates once every 5.27 hours and has no discernible moons.

The asteroid's density is approximately 1.55 ounces per cubic inch (2.7 grams per cubic centimeter), close to the average density of Earth's crust. This makes Eros about twice as dense as asteroid 253 Mathilde, a C-type, carbon-rich asteroid that NEAR flew past in June 1997, and about the same density as S-type asteroid 243 Ida, which NASA's Galileo spacecraft flew past in 1993. Eros and Ida are the only S-type asteroids for which a mass and density have been determined.

Flyby imaging of the asteroid's surface revealed a prominent elongated ridge that extends along its length for as much as 12 miles (20 km). "This ridge-like feature, combined with the measurements of high density, suggests that Eros is a homogeneous body rather than a collection of rubble" such as Mathilde appears to be, said Dr. Joseph Veverka, of Cornell University, Ithaca, NY, who heads the mission's imaging team. "It might even be a remnant of a larger body that was shattered by an impact."

The surface of Eros is pocked with craters. The two largest craters are four miles and 5.3 miles (8.5 and 6.5 km) in diameter, less than half the size of asteroid Mathilde's largest craters. The existence of fewer, smaller craters could be an indication that Eros has a relatively young surface when compared to Ida.

NEAR and Eros will cross paths again in February 2000. The spacecraft will then be inserted into orbit around the asteroid and begin its yearlong study. Images taken during orbit are expected to have more than 200 times better resolution than those obtained during the flyby and will be taken from as close as nine miles (15 km) from the asteroid's surface.

Flyby images of Eros and a related movie, a shape model of the asteroid, and a chart of spectral observations are available on the NEAR mission Web site at:

http://near.jhuapl.edu

The Applied Physics Laboratory is a not-for-profit laboratory and independent division of The Johns Hopkins University. APL conducts research and development primarily for national security and for nondefense projects of national and global significance. APL is located midway between Baltimore and Washington, D.C. in Laurel, Md.


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 Reveals Major Features Of Eros Asteroid." ScienceDaily. ScienceDaily, 9 February 1999. <www.sciencedaily.com/releases/1999/02/990209073240.htm>.
Johns Hopkins University Applied Physics Laboratory. (1999, February 9). Near Spacecraft Reveals Major Features Of Eros Asteroid. ScienceDaily. Retrieved July 23, 2014 from www.sciencedaily.com/releases/1999/02/990209073240.htm
Johns Hopkins University Applied Physics Laboratory. "Near Spacecraft Reveals Major Features Of Eros Asteroid." ScienceDaily. www.sciencedaily.com/releases/1999/02/990209073240.htm (accessed July 23, 2014).

Share This




More Space & Time News

Wednesday, July 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Cargo Craft Undocks from Space Station

Raw: Cargo Craft Undocks from Space Station

AP (July 22, 2014) A Russian Soyuz cargo-carrying spacecraft undocked from the International Space Station on Monday. The craft is due to undergo about ten days of engineering tests before it burns up in the Earth's atmosphere. (July 22) Video provided by AP
Powered by NewsLook.com
NASA Ceremony Honors Moon Walker Neil Armstrong

NASA Ceremony Honors Moon Walker Neil Armstrong

AP (July 21, 2014) NASA honored one of its most famous astronauts Monday by renaming a historic building at the Kennedy Space Center in Florida. It now bears the name of Neil Armstrong, the first man to walk on the moon. (July 21) Video provided by AP
Powered by NewsLook.com
Neil Armstrong's Post-Apollo 11 Life

Neil Armstrong's Post-Apollo 11 Life

Newsy (July 19, 2014) Neil Armstrong gained international fame after becoming the first man to walk on the moon in 1969. But what was his life like after the historic trip? Video provided by Newsy
Powered by NewsLook.com
This Week @ NASA, July 18, 2014

This Week @ NASA, July 18, 2014

NASA (July 18, 2014) Apollo 11 yesterday, Next Giant Leap tomorrow, Science instruments for Europa mission, and more... Video provided by NASA
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:
from the past week

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