A student-professor team at Nebraska Wesleyan University has helped uncover evidence of complex molecules on the surface of Pluto, a find that could explain the dwarf planet's ruddy color.

"This is further evidence of the types of molecules that may be making Pluto reddish," said Physics Professor Nathaniel Cunningham.

Along with student Mitch Hain and researchers at the Southwest Research Institute in San Antonio, Cunningham studied data provided by the Hubble Space Telescope this summer to better understand Pluto's composition. The Hubble's highly sensitive Cosmic Origins Spectograph generated the data used by the team.

The team found a strong ultraviolent wavelength absorber on Pluto's surface, suggesting possible complex hydrocarbon and nitrile molecules on the planet's surface. The molecules aren't signs of life on the distant planet and can be produced by interaction of sunlight or cosmic rays with Pluto's known surface ices, including methane, carbon monoxide and nitrogen.

The team also discovered evidence of changes in Pluto's ultraviolet spectrum compared to Hubble measurements from the 1990s. The changes may be related to differing terrains seen now versus then, or to other effects, such as changes in the surface related to a steep increase in the pressure of Pluto's atmosphere during that same time span.

Cunningham said the team's research may be used to help plan research conducted by NASA when its New Horizons spacecraft reaches Pluto in 2015. The Astronomical Journal recently published the team's findings.

Alan Stern of the Southwest Research Institute said the team's research bodes well for NASA's New Horizons mission.

"The discovery we made with Hubble reminds us that even more exciting discoveries about Pluto's composition and surface evolution are likely to be in store when NASA's New Horizons spacecraft arrives at Pluto," Stern said.

Hain, who is now studying mechanical engineering at Washington University in St. Louis, said his role was to pore through the data taken from the Hubble to search for meaningful results.

"It was a good project to wrap up my career at Wesleyan," he said.

​Reach Kevin Abourezk at 402-473-7225 or kabourezk@journalstar.com.