The discovery of another bright light on the dwarf planet Ceres has NASA scientists perplexed as the US Dawn probe prepares to enter the orbit of the largest object in the asteroid belt and possibly resolve the mystery.

The images taken nearly 29,000 miles (46,000 kilometers) from Ceres show that a bright spot on the planet scientists previously discovered appears next to another slightly darker spot, NASA said in a news release.

The light appears in the same basin as the other spot, images released by NASA show.

"This may be pointing to a volcano-like origin of the spots, but we will have to wait for better resolution before we can make such geologic interpretations," Chris Russell from the Dawn mission said.

The Dawn probe will enter the orbit of Ceres March 6. Scientists expect to receive better views of the mystery lights as the spacecraft closes in and spirals nearer the dwarf planet.

"The brightest spot continues to be too small to resolve with our camera, but despite its size it is brighter than anything else on Ceres. This is truly unexpected and still a mystery to us," said scientist Andreas Nathues who is in charge of the camera.

Scientists detected water vapor emitting from Ceres in 2012 and NASA reports the surface of the body contains "water-bearing minerals."

Launched in 2007, the Dawn probe was sent to investigate the two largest bodies in the asteroid belt, which lies between Mars and Jupiter.

Dawn explored giant asteroid Vesta starting in 2011, providing measurements and images. After 2012, the probe left Vesta's orbit and began its journey to Ceres.

Ceres has a diameter of about 590 miles (950 kilometers) and Vesta has a diameter of about 326 miles (525 kilometers).