433 Eros

Infobox Planet | discovery=yes | physical_characteristics = yes | bgcolour=#FFFFC0
name=433 Eros


caption= View from one end of Eros across the gouge on its side towards the opposite end.
discoverer=Carl Gustav Witt
discovered = August 13, 1898
alt_names = 1898 DQ; 1956 PC
mp_category = Amor,
Mars-crosser asteroid
epoch=October 22, 2004 (JD 2453300.5)
semimajor=218.155 Gm (1.458 AU)
perihelion=169.548 Gm (1.133 AU)
aphelion=266.762 Gm (1.783 AU)
eccentricity=0.223
period=643.219 d (1.76 a)
inclination=10.829°
asc_node=304.401°
arg_peri=178.664°
mean_anomaly=320.215°
avg_speed = 24.36 km/s
dimensions=13×13×33 km
mass=7.2×10¹⁵ kg
density=2.4 g/cm³
surface_grav = 0.0059 m/s²
escape_velocity=0.0103 km/s
rotation=0.2194 d (5 h 16 min)
spectral_type=S
magnitude = +7.1 to +15
abs_magnitude = 11.16
albedo=0.16
single_temperature = ~227 K

433 Eros (pronEng|ˈɪərɒs "irr'-os") is the first discovered Near-Earth asteroid, named after the Greek god of love, Eros (Greek Ἔρως). It is an S-type asteroid approximately 13 × 13 × 33 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 dinosaurs.Fact|date=July 2008 [Dividing the mass of 433 Eros by its density gives a volume of 3000 km³, while the estimated 5 km radius of the (assumed spherical) Chicxulub Crater impactor yields a volume of only about 520 km³.Or|date=July 2008]

Eros 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. [Michel P. et al. [http://www.nature.com/nature/journal/v380/n6576/abs/380689a0.html The orbital evolution of the asteroid Eros and implications for collision with the Earth] , Nature (journal)]

The rarely-used adjectival form of the name Eros is "Erotian" (pronEng|ɪˈroʊʃən).

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 meteorite 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.cite journal | author=Thomas PC, Robinson MS | title=Seismic resurfacing by a single impact on the asteroid 433 Eros | journal=Nature| volume=436| issue=7049 | year=1970 | pages=366–9 | doi=10.1038/nature03855 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.

Eros contains more gold than the total amount of gold ever extracted on Earth. [ [http://news.bbc.co.uk/1/hi/sci/tech/401227.stm] (English)]

History

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 [Scholl, Hans and Lutz D. Schmadel, "Discovery Circumstances of the First Near-Earth Asteroid (433) Eros", "Beiträge zur Astronomiegeschichte", vol. 5, p. 210-220 (2002)] . Witt was taking a 2 hour exposure of Beta Aquarii to secure astrometricpositions of asteroid 185 Eunike. [Donald K. Yeomans. [http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/31429/1/95-1108.pdf Asteroid 433 Eros: The Target Body of the NEAR Mission ] , Jet Propulsion Laboratory/California Institute of Technology.]

During the opposition of 1900-1901, a world-wide 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 [Hinks, A. R., "Solar Parallax Papers No. 7: The General Solution from the Photographic Right Ascensions of Eros, at the Opposition of 1900", "Monthly Notices of the Royal Astronomical Society" v. 69, no. 7, pp. 544 ff. (1910)] . A similar program was then carried out, during a closer approach, in 1930-1931 by Harold Spencer Jones [Jones, H. Spencer, "The Solar Parallax and the Mass of the Moon from Observations of Eros at the Opposition of 1931", "Memoirs of the Royal Astronomical Society", v. LXVI, part II (1941)] . 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) with a visual magnitude of +8.5. But 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. [ [http://www.erosproject.com/appeal/apindex.html The Eros Project] ]

ee also

*Eros Day
*Eros in fiction
*List of geological features on 433 Eros

References and Notes

External links

* [http://near.jhuapl.edu/ NEAR Shoemaker spacecraft]
* [http://near.jhuapl.edu/iod/archive.html NEAR image of the day archive]
* [http://near.jhuapl.edu/iod/20010731/index.html Movie: NEAR Shoemaker spacecraft landing]
* [http://www.erosproject.com The Eros Project] (OrbDev's attempts at litigation over their property claim)
*JPL Small Body
* [http://newton.dm.unipi.it/cgi-bin/neodys/neoibo?objects:Eros;ephpred NEODys] [http://home.comcast.net/~kpheider/433Eros.txt (saved output file)] showing distance and magnitude Ephemerides for Eros during rare oppositions