A large space rock that zipped past Earth on Halloween on October 31 was most likely a dead comet that fittingly bears an eerie resemblance to a skull.

Scientists observing asteroid named 2015 TB145 determined that the celestial object was more than likely a dead comet that has shed its volatiles after numerous passes around the Sun, NASA said in a statement.

The belated comet has also been observed by optical and radar observatories around the world, providing even more data, including first close-up views of its surface.

Asteroid 2015 TB145 safely flew by earth at just under 1.3 lunar distances, or about 486,000 km, on October 31.

The first radar images of the dead comet were generated by the National Science Foundation’s Arecibo Observatory in Puerto Rico.

“We found that the object reflects about six percent of the light it receives from the sun,” added Vishnu Reddy, research scientist at the Planetary Science Institute, Tucson, Arizona.

“That is similar to fresh asphalt, and while here on Earth we think that is pretty dark, it is brighter than a typical comet which reflects only 3 to 5 percent of the light. That suggests it could be cometary in origin — but as there is no coma evident, the conclusion is it is a dead comet.”

Asteroid 2015 TB145 was discovered on October 10 this year by the University of Hawaii’s Pan-STARRS-1 (Panoramic Survey Telescope and Rapid Response System) on Haleakala, Maui, Hawaii.

The next time the asteroid will be in Earth’s neighbourhood will be in September 2018, when it will make a distant pass at about 38 million km or about a quarter the distance between Earth and the sun.