According to NASA’s Center for NEO Studies (CNEOS), on 5th March asteroid called TX68 will pass near Earth in possible closest range of 17000 km.
TX68 is small asteroid spotted on October 6, 2013 by Catalina Sky Survey. It was discovered when it was four and half-length of moon distance from Earth (distance to the moon is 384399 km). It was described as twice larger than infamous Chelyabinsk asteroid which caused heavy panic in Russia on 15 February 2013. Its diameter in widest point is 52 m in narrowest - 21 m. CNEOS in press announcement by its manager, Paul Chodas assured:
“The possibilities of collision on any of the three future flyby dates are far too small to be of any real concern. I fully expect any future observations to reduce the probability even more… This asteroid’s orbit is quite uncertain, and it will be hard to predict where to look for it. There is a chance that the asteroid will be picked up by our asteroid search telescopes when it safely flies past us next month, providing us with data to more precisely define its orbit around the sun.”
Asteroid is not any kind of danger to Earth but due the fact, that its Sun orbit is not well constrained, it is hard to predict exact distance from Earth. Most probable is that closest possible distance from Earth to TX68 will be reached on 5th March. On this day asteroid will fly only 17000 km from Earth - it means that it will be 20 times closer than Moon. But it should be considered as lowest possible distance - it is also possible that it will fly 14 million km from Earth. Possibility of direct impact of TX68 to Earth on March 2016 is, according to CNEOS, equal to zero. However in further years possibility of impact will exist but still on very low level. On 28 September 2017 it is predicted for 1 to 260 million, on 27 September 2046 it is described as 1 to 8 billion and on 27 October 2097 it will be 1 to 5.3 billion. Combined possibility is still very low: 1 to 244 million. In spite of this fact, it is worth to mention that TX68 is small asteroid and Planetary Defense Coordination Office (PDCO) (NASA office for coordinating efforts for searching for NEO potentially danger for Earth) is not considering it as a threat. Only asteroids larger than 140 m in diameter are considered as danger. TX68 even in case of impact would probably cause large fireball in the sky and created crater with diameter with range 100–575 meters. Comparing to Chelyabinsk asteroid, potential danger could be considered as twice as big, but still in global scale it should not be reason to worry. More about ways of preventing and spotting asteroids You can read here and here.