|Discovery site||Observatorio Astronómico de La Sagra|
|Discovery date||14 July 2007|
|Epoch 13 January 2016 (JD 2457400.5)|
|Uncertainty parameter 0|
|Observation arc||6296 days (17.24 yr)|
|Aphelion||1.6061055 AU (240.26996 Gm)|
|Perihelion||1.4414495 AU (215.63778 Gm)|
|1.5237775 AU (227.95387 Gm)|
|1.88 yr (687.04 d)|
(311999) 2007 NS2 was discovered on 14 July 2007, by the Observatorio Astronómico de La Sagra. Its orbit is characterized by low eccentricity (0.054), moderate inclination (18.6°) and a semi-major axis of 1.52 AU. Upon discovery, it was classified as Mars-crosser by the Minor Planet Center. Its orbit is well determined as it is currently (March 2013) based on 87 observations with a data-arc span of 4,800 days. 2007 NS2 has an absolute magnitude of 17.8, which gives a characteristic diameter of 870 m.
Jean Meeus suspected that (311999) 2007 NS2 was a Mars Trojan, and this was confirmed by Reiner Stoss's analysis of two sets of observations dating from 1998 on the MPC database. It was confirmed to be a Mars Trojan numerically in 2012. Recent calculations confirm that it is a stable L5 Mars Trojan asteroid with a libration period of 1310 years and an amplitude of 14°. These values as well as its short-term orbital evolution are similar to those of 5261 Eureka. Out of all known Mars Trojans, it currently has the smallest relative (to Mars) semimajor axis, 0.000059 AU.
Long-term numerical integrations show that its orbit is very stable on Gyr time-scales (1 Gyr = 1 billion years). As in the case of Eureka, calculations in both directions of time (4.5 Gyr into the past and 4.5 Gyr into the future) indicate that (311999) 2007 NS2 may be a primordial object, perhaps a survivor of the planetesimal population that formed in the terrestrial planets region early in the history of the Solar System.