Comet P/2016 BA14 flew past Earth last March 22 in the third closest comet flyby ever recorded. It hurtled past the planet about 2.2 million miles away at the time of its closest approach.

Thanks to radar and infrared technology, NASA was able to image the flyby and track the comet also known as PanSTARRS.

The Goldstone Solar System Radar, situated in the Mojave Desert in California, tracked the comet and imaged it to be about 3,000 feet (1 kilometer) in diameter. The radar produced highly detailed images of the comet nucleus over three days around the period of its closest approach.

“We can see surface features as small as 8 meters (26 feet) per pixel,” reports NASA researcher Shantanu Naidu, who led the observations during the flyby.

The radar images revealed PanSTARRS’s irregular shape: a brick-like appearance on one side and a pear-like one on the other. They also featured the comet’s topography made up of small concavities, massive flat regions and ridges present on the nucleus surface. New observations, too, showed that the comet seems to spin around its own axis every 35 to 40 hours.

NASA’s Infrared Telescope Facility located in Mauna Kea, Hawaii, also lent a close look at PanSTARRS. Collected data indicated that the heavenly body reflects 2 to 3 percent of the sunlight falling on the surface, with nuclei likened to fresh asphalt, which reflects only around 4 percent of the light falling on it.

This is quite common among comets, said Vishnu Reddy of Arizona’s Planetary Science Institute, adding that they estimate the comet’s size to be from 600 meters to 1.2 kilometers (0.4 miles to 0.75 miles) in diameter, which is consistent with the radar imaging.

Originally discovered as an asteroid, PanSTARRS was later on detected to have comet-like properties when its orbit was found to be similar to that of another comet, 252P/LINEAR, which also made a close flyby of the planet at 3.3 million miles last March 21.

Data from the Discovery Channel Telescope suggested that the two bodies may have once been sections of a bigger object that had broken apart.

Infrared spectra are hoped to provide clues on the makeup of these primitive inhabitants of the solar system. Scientists dubbed it an extremely rare chance to study two comets with historically close flybys, assisting them in measuring the comets’ physical characteristics and understanding cometary evolution.

The last comet to come closest to the planet was Lexell’s comet, which flew by Earth at a 1.4-million-mile distance on July 1, 1770. The observers of that era had a glimpse of the heavenly body almost as bright as Saturn, stretching out across the sky four times as wide as a full moon.

Unfortunately, PanSTARRS a couple of days ago was not visible to the naked eye, and one would have needed a backyard instrument or telescope. The presence of the moon, too, naturally drowned out views of the comets.