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Six different views of Eros in approximate natural color by NEAR-Shoemaker in February 2000
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Discovery
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| Discovered by | Carl Gustav Witt |
| Discovery date | August 13, 1898 |
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Designations
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| Named after | Eros |
| Alternate name(s) | 1898 DQ; 1956 PC |
| Minor planet category |
Amor, Mars-crosser asteroid |
| Adjective | Erotian |
| Epoch October 22, 2004 (JD 2453300.5) | |
| Aphelion | 1.783 AU (266.762 Gm) |
| Perihelion | 1.133 AU (169.548 Gm) |
| Semi-major axis | 1.458 AU (218.155 Gm) |
| Eccentricity | 0.223 |
| Orbital period | 1.76 a (643.219 d) |
| Average orbital speed | 24.36 km/s |
| Mean anomaly | 320.215° |
| Inclination | 10.829° |
| Longitude of ascending node | 304.401° |
| Argument of perihelion | 178.664° |
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Physical characteristics
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| Dimensions | 34.4×11.2×11.2 km[1][2] 16.84 km[1] |
| Mass | 6.69×1015 kg[2] |
| Mean density | 2.67±0.03 g/cm³[1][2] |
| Equatorial surface gravity | 0.0059 m/s² |
| Escape velocity | 0.0103 km/s |
| Rotation period | 0.2194 d (5 h 16 min) |
| Albedo | 0.25[1] |
| Temperature | ~227 K |
| Spectral type | S[1] |
| Apparent magnitude | +7.0[3] to +15 |
| Absolute magnitude (H) | 11.16[1] |
433 Eros is a near-Earth asteroid (NEA) discovered in 1898, and the first asteroid to be orbited by a probe (in 2000). It is an S-type asteroid approximately 34.4×11.2×11.2 km in size, the second-largest NEA after 1036 Ganymed, and belongs to the Amor group.
Eros is a Mars-crosser asteroid, the first known to come within the orbit of Mars. Objects in such an orbit can remain there for only a few hundred million years before the orbit is perturbed by gravitational interactions. Dynamical integrations suggest that Eros may evolve into an Earth-crosser within as short an interval as 2 million years, and has a roughly 50% chance of doing so over a time scale of 108–109 years.[4] It is a potential Earth impactor,[4] believed to be larger than the impactor that created the Chicxulub Crater that led to the extinction of the dinosaurs.[5]
The NEAR Shoemaker probe visited Eros twice, first with a 1998 flyby, and then by orbiting it in 2000 when it extensively photographed its surface. On February 12, 2001, at the end of its mission, it landed on the asteroid's surface using its maneuvering jets.
The rarely used adjectival form of the name Eros is Erotian ( /ɪˈroʊʃən/). Eros is pronounced /ˈɪərɒs/ irr-os and the Greek is Ἔρως. It is named after the Greek god of love, Eros.
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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.[6]
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.[6]
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.[7] Witt was taking a 2-hour exposure of Beta Aquarii to secure astrometric positions of asteroid 185 Eunike.[8]
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.[9] A similar program was then carried out, during a closer approach, in 1930–1931 by Harold Spencer Jones.[10] 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.
On January 31, 2012, Eros will pass the Earth at 0.17867 AU (26,729,000 km; 16,608,000 mi),[11][12] about 70 times the distance to the Moon, with a visual magnitude of +8.1.[13] During rare oppositions, every 81 years, such as in 1975 and 2056, Eros can reach a magnitude of +7.0,[3] 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.
In an experimental legal case, Eros was claimed as property by Gregory W. Nemitz of OrbDev. Nemitz argued that, according to the homestead principle, 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. An expert in extraterrestrial real estate issues, Virgiliu Pop, responded by using the same novelty-deed registry Nemitz had used for Eros to claim ownership of the Sun, stating:
I, for one, intended this move only to show how ridiculous a property rights system in outer space would be if it were to be based solely on claim unsubstantiated by any actual possession.—Virgiliu Pop [14]
Nemitz's case was dismissed and an appeal denied.[15]
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