433 Eros ( ) is the first discovered
Near-Earth asteroid, named after the
Greek god of
love,
Eros (
Greek Ἔρως). It is an
S-type asteroid approximately 34.4×11.2×11.2 km in size, the second-largest
near-Earth asteroid (NEA) after
1036 Ganymed, belonging to the
Amors. It is a
Mars-crosser asteroid and was the first asteroid that was known to come within the orbit of Mars. Eros is one of the few NEAs with a maximum diameter greater than 10 km. It is believed to be larger than the impactor that created
Chicxulub Crater in the
Yucatán, which has been linked to the
extinction of the dinosaursEros was visited by the
NEAR Shoemaker probe, which orbited it, taking extensive photographs of its surface, and, on February 12, 2001, at the end of its mission, landed on the asteroid's surface using its maneuvering jets.
Objects in an orbit like Eros can exist for only a few hundred million years before the orbit is perturbed by gravitational interactions. Simulations suggest that Eros may evolve into an Earth-crosser within 2 million years.
The rarely used adjectival form of the name Eros is
Erotian ().
Physical characteristics
Surface gravity depends on the distance from a spot on the surface to the center of a body's mass. The Erotian surface gravity varies greatly, since Eros is not a sphere but an elongated peanut-shaped (or potato- or shoe-shaped) object. The daytime temperature on Eros can reach about 100 °C at
perihelion. Nighttime measurements fall near -150 °C. Eros's density is 2,400
kg/m3, about the same as the density of Earth's crust. It rotates once every 5.27 hours.
NEAR scientists have found that most of the larger rocks strewn across Eros were ejected from a single crater in a meteor collision approximately 1 billion years ago. This impact may also be responsible for the 40 percent of the Erotian surface that is devoid of craters smaller than 0.5 kilometers across. It was originally thought that the debris thrown up by the collision filled in the smaller craters. An analysis of crater densities over the surface indicates that the areas with lower crater density are within 9 kilometers of the impact point. Some of the lower density areas were found on the opposite side of the asteroid but still within 9 kilometers.
[ PMID 16034412]It is theorized that
seismic shockwaves propagated through the asteroid, shaking smaller craters into rubble. Since Eros is irregularly shaped, a 9 kilometer straight line through the asteroid can reach locations that would be further away if travelling across the surface, thus leading to the uneven pattern of crater density on the surface.
It is theorized that Eros has more
gold,
silver,
zinc,
aluminium and other metals than have ever been, or could ever be, mined from the upper levels of Earth's
crust.
History
Animation of the rotation of Eros.
As one of the larger
Near Earth Asteroids (NEAs), Eros has played a significant role in history. It was discovered on the same night (13 August 1898) by
Gustav Witt in Berlin and
Auguste Charlois at Nice. Witt was taking a 2 hour exposure of
Beta Aquarii to secure astrometric positions of asteroid
185 Eunike.
During the opposition of 1900–1901, a worldwide program was launched to make
parallax measurements of the asteroid to determine the
solar parallax (or distance to the sun), with the results published in 1910 by
Arthur Hinks of
Cambridge. A similar program was then carried out, during a closer approach, in 1930–1931 by
Harold Spencer Jones. The value obtained by this program was considered definitive until 1968, when greater faith was placed in
radar and
dynamical parallax methods.
Eros was one of the first asteroids to be visited by a spacecraft, and the first to be orbited and soft-landed on.
NASA spacecraft
NEAR Shoemaker entered orbit around Eros in 2000, and came to rest on its surface in 2001.
Visibility from Earth
On January 31, 2012 Eros is expected to pass Earth at 0.179
astronomical units (16.6 million miles), about 70 times the distance to the moon, with a
visual magnitude of +8.5. During rare oppositions, every 81 years, such as in 1975 and 2056, Eros can reach a magnitude of +7.1, which is brighter than
Neptune and brighter than any
main belt asteroid except
4 Vesta and, rarely
2 Pallas and
7 Iris. Under this condition, the asteroid actually appears to stop, but unlike the normal condition for a body in heliocentric conjunction with the Earth, it never appears to be
retrograde. Its
synodic period of over 846 Earth days is among the largest of any body in the Solar System.
Legal controversy
In an experimental legal case, Eros was claimed as property by Gregory W. Nemitz of OrbDev. According to the
Homestead principle, Nemitz argued that he had the right to claim ownership of any celestial body that he made use of; he claimed he had designated Eros a spacecraft parking facility and wished to charge
NASA a parking and storage fee of twenty cents per year for NEAR Shoemaker. Nemitz's case was dismissed and an appeal denied.
See also
