Asteroid 2015 DS passed by the Earth at a distance of 6 590 000 km (17.1 times the average distance between the Earth and the Moon, or 4.40% of the average distance between the Earth and the Sun), slightly before 10.55 am GMT on Monday 9 March 2015. There was no danger of the asteroid hitting us, though had it done so it would have presented only a minor threat. 2015 DS has an estimated equivalent diameter of 20-62 m (i.e. it is estimated that a spherical object with the same volume would be 20-62 m in diameter), and an object of this size would be expected to explode in an airburst (an explosion caused by superheating from friction with the Earth's atmosphere, which is greater than that caused by simply falling, due to the orbital momentum of the asteroid) in the atmosphere between 22 and 5 km above the ground, with only fragmentary material reaching the Earth's surface, although since an object at the upper end of this range would be expected to release an amount of energy equivalent to about 12 megatons of TNT (roughly 700 times the energy released by the Hiroshima bomb), then being directly underneath it might be fairly unpleasant.
The calculated orbit of 2015 DS. JPL Small Body Database.
2015 DS was discovered on 17 February 2015 (twenty days before its closest approach to the Earth) by the University of Arizona's Catalina Sky Survey, which is located in the Catalina Mountains north of Tucson. The designation 2015 DO215 implies that it was the 18th asteroid (asteroid S) discovered in the second half of February 2015 (period 2015 D).
While 2015 DS occasionally comes near to the Earth, it does not actually cross our orbital path. It has an elliptical 567 day orbit, at an angle of 3.42° to the plane of the Solar System, that takes it from 1.02 AU from the Sun (1.02 times the average distance at which the Earth orbits the Sun), slightly outside our orbit, to 1.66 AU from the Sun, (1.66 times the distance at which the Earth orbits the Sun and outside the orbit of the planet Mars). As a Near Earth Object that remains strictly outside the orbit of the Earth it is classed as an Amor Family Asteroid. This orbit also means that close encounters between 2015 DS and the Earth are extremely common, with the last having occured in July 2012 and the next predicted for November 2017. 2015 DS is also calculated to have fairly frequent close encounters with the planet Mars, with the last having occurred in August 1994 and the next predicted for April 2037.
See also...
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