Near-Earth Asteroids
	Potentially Hazardous Asteroids (PHAs) are space rocks larger than approximately 100m that can come closer to Earth than 0.05 AU. None of the known PHAs is on a collision course with our planet, although astronomers are finding new ones all the time. On March 17, 2009 there were 1043 potentially hazardous asteroids. March 2009 Earth-asteroid encounters: Asteroid Date(UT) Miss Distance Mag. Size 2009 DS43 Mar. 1 6.9 LD 18 32 m 2009 DD45 Mar. 2 0.2 LD 11 35 m 2009 DN4 Mar. 3 8.1 LD 21 27 m 2009 EA Mar. 4 7.4 LD 19 24 m 2009 EW Mar. 6 0.9 LD 16 23 m 161989 Cacus Mar. 7 70.5 LD 16 1.7 km 2009 EH1 Mar. 8 1.6 LD 18 12 m 2009 ET Mar. 9 9.5 LD 21 15 m 2009 DV43 Mar. 10 8.5 LD 18 80 m 2009 EU Mar. 11 3.5 LD 18 21 m 1998 OR2 Mar. 12 69.8 LD 14 3.3 km 2009 DR3 Mar. 14 7.2 LD 16 225 m 2009 FH Mar. 18 0.2 LD 14 21 m Notes: LD means "Lunar Distance." 1 LD = 384,401 km, the distance between Earth and the Moon. 1 LD also equals 0.00256 AU. MAG is the visual magnitude of the asteroid on the date of closest approach. Note: In March of this year, two PHA's having a footprint in excess of 21 meters across have passed within 4800 miles of Earth. However, a Torino rating of zero was assigned to both, meaning neither posed any threat to the planet, since if they were to intersect the Earth's orbit, they would have burned up in the atmosphere before landing.