by Kim Malville
What’s happening in the skies this month?
March 1: The Red Planet Mars becomes retrograde. Watch it move relative to Spica, from east to west.
March 3: Saturn reaches its stationary point and begins retrograde.
March 6: Jupiter has ceased its retrograde motion. On this day it is stationary, moving neither to the east nor to the west. Tomorrow it starts slowly moving direct, eastward, among the stars.
March 9: Jupiter lies above the moon, which is above Orion. There’s nearly a straight line connecting Jupiter, the moon, and Betelgeuse.
March 17/18: The moon, Spica, and Mars form a beautiful triangle.
March 20: The sun crosses the celestial equator at 10:57am MDT, establishing Vernal Equinox.
The lost asteroid
Last month we learned that a Near-Earth Asteroid (NEO), 2000 EM26, measuring 885’ across and traveling at a speed of 27,000 miles per hour would buzz our planet on February 17/18. The encouraging word was there is utterly no chance of collision since it will miss our planet by a safe margin of 2million miles, something like nine times the distance of the moon.
Remote controlled telescopes on the Canary Islands, off the coast of West Africa, were all set to photograph its approach. Now, as I write this, a week after its predicted approach that asteroid called Moby Dick by some astronomers, has gone missing. When a robotic telescope in the Canary Islands turned to the predicted position, the asteroid was nowhere to be found.
This potentially close encounter comes a year after two unusual asteroid events which occurred on February 15, 2013. That’s when 98’-wide asteroid 2012 DA14 buzzed by our planet. The office-building sized chunk of rock came closer to Earth than most orbiting communication and weather satellites. Coincidentally, that same day another 65’-wide meteor exploded above the central Russian city of Chelyabinsk.
So what did happen to asteroid 2000 EM26? The most likely scenario is that it is on a slightly different path from its expected trajectory, and the telescope wasn’t looking in the right place. Asteroid 2000 EM26 was discovered 14 years ago and has not been seen since, so astronomers have limited information about it. Not knowing enough about how the asteroid rotates makes it hard to know how other forces, like radiation pressure from sunlight might nudge the rock onto a different trajectory. The asteroid may simply too dark in color to see easily. Actually, Moby Dick is misnamed. Even though it’s a whale of a rock, it is not white, but as dark as coal: chalk up one for poetic license!
The word from NASA is “Don’t Panic”. Asteroids 65’ in diameter like the one that hit the atmosphere above Chelyabinsk attack our planet only once or twice a century. Most fall over oceans or unpopulated areas like the Antarctic. NASA has been charged by Congress to locate Potentially Hazardous Asteroids (PHAs), although recent cuts in their budget make the task difficult. PHAs come threateningly close to the Earth, within 4,650,000 miles, with a diameters larger than 500’ in diameter. There are currently 1458 known PHAs of which Moby Dick is one. If you were living on Mars, I’d advise you to panic.
An asteroid hits Mars
Last month I reported on the peculiar rock photographed by Opportunity on Mars that appeared out of nowhere. It could have been a meteorite that landed nearby, which was not very likely because there was no impact crater. It could have been a low velocity rock ejected from nearby meteor impact. Now, it appears to be roadkill. What a letdown, roadkill! The rock apparently was kicked up by the wheels of the rover. If only Crestone still had the Roadkill Cafe, a photo of this Martian rock could festoon its walls.
But asteroids do rain down on Mars. A NASA satellite orbiting Mars has detected a new crater some 100’ in diameter and surrounded by a blast zone that is as wide as 9.3 miles. The impressive crater was produced in a dune field, sometime in the period July 2010 and May 2012. Impacts producing craters this large occur at a rate of about 200 per year across the planet. That’s a lot! Mars is a dangerous place for two reasons. It is at the inner edge of the asteroid belt and a slight nudge of one of those rocks could send it easily hurtling onto the Red Planet. Secondly, Mars has a very thin atmosphere, so smaller rocks are not incinerated like they are in our atmosphere. Be grateful you are an Earthling.
Curiosity in search of life on Mars
Landing on the surface of Mars in mid-2012, the Curiosity rover is combing its surface for clues of ancient or modern life. Recent findings by Curiosity include evidence for an ancient freshwater lake, and the disappointing lack of evidence for methane, which could have been evidence of real but primitive life on the planet. To continue its investigation, the car-sized rover is planning to drive up Mt. Sharp, the central peak of the large crater in which it landed. The mountain is named after Robert Sharp, a legendary geology professor at Caltech. In order to avoid more dangerous and rocky terrain, Curiosity was directed to drive through a gap in a high sand dune that had blocked a useful entrance to Mt. Sharp. After completing this trip though Dingo Gap, the robotic rover looked backward and took this picture showing the sand mound covered with its wheel tracks. The pictures gives a wonderful sense of what it would be like to visit Mars. Does it remind anyone else of the four-wheel road toward Medano Pass in the Great Sand Dunes?