"Cantor noticed an inconspicuous dark dot near the equator in one of the images about two months back."
Washington, May 23 - Researchers have discovered the largest fresh meteor-impact crater on Mars, NASA said in a statement.
The before-and-after images of the crater were captured by NASA's Mars Reconnaissance Orbiter (MRO).
The crater is half the size of a football ground and first appeared in March 2012, the US space agency said.
It was captured by the orbiter's weather-monitoring camera, the Mars Color Imager (MARCI).
Studies of fresh impact craters on Mars yield valuable information about impact rates and about subsurface material exposed by the excavations, said Leslie Tamppari, deputy project scientist at NASA's Jet Propulsion Laboratory (JPL) in California.
The impact that created the crater was probably preceded by an explosion in the Martian sky caused by intense friction between an incoming asteroid and the planet's atmosphere, the Nasa release added.
The creation of the crater may be compared with the meteor blast that shattered windows in Chelyabinsk, Russia, last year.
The air burst and ground impact darkened an area of the Martian surface about 8 km across.
Since the orbiter began its systematic observation of Mars in 2006, Bruce Cantor, who is the camera's deputy principal investigator at Malin Space Science Systems, has examined MARCI's daily global coverage.
Cantor noticed an inconspicuous dark dot near the equator in one of the images about two months back.
Once verified as new, the dark spot was targeted by CTX and the orbiter's sharpest-sighted camera, the High Resolution Imaging Science Experiment (HiRISE), the statement said.