5261 EUREKA

'5261 Eureka' was discovered at Mt Palomar on June 20, 1990 and turned out to be the first known Mars Trojan asteroid. It trails Mars (at the L₅ point) at a distance varying by only 0.3 AU during each revolution (with a secular trend superimposed, changing the distance from 1.5-1.8 AU around 1850 to 1.3-1.6 AU around 2400). Minimum distances from the Earth, Venus and Jupiter are 0.5, 0.8 and 3.5 AU, respectively.
Long-term numerical integration shows that the orbit is stable. Kimmo A. Innanen and Seppo Mikkola note that "contrary to intuition, there is clear empirical evidence for the stability of motion around the L₄ and L₅ points of all the terrestrial planets over a timeframe of several million years".
Since the discovery of 5261 Eureka, the Minor Planet Center has recognized three other asteroids as Martian Trojans: at the L point, at the L point,[1] and , also at the L point.[2] At least six other asteroids have been discovered which are in near 1:1 resonances with Mars, but fail to exhibit trojan behavior. They are , , , , and .[3][4]
The infrared spectrum for 5261 Eureka is typical of an A-class asteroid, but the visual spectrum is consistent with an evolved form of achondrite called an angrite. A-class asteroids are tinted red in hue, with a moderate albedo. The asteroid is located deep within a stable Lagrangian zone of Mars, which is considered indicative of a primordial origin —meaning the asteroid has most likely been in this orbit for much of the history of the solar system.

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References

References

★ IAUC 5045

★ IAUC 5047

★ IAUC 5067

★ IAUC 5075

★ A. S. Rivkin, R. P. Binzel, S. J. Bus, and J. A. Grier, "Spectroscopy and Classification of Mars Trojan Asteroids", ''Bulletin of the American Astronomical Society'' 34, 2002, p. 840.

★ S. Tabachnik and N. W. Evans, "Cartography for Martian Trojans", ''The Astrophysical Journal'' 517, 1999, pp. L63-L66.