"We have made the fastest crossing of the Atlantic Ocean by a solar boat and the longest distance ever covered by a solar electric vehicle, " said Domjan.

CNN: STORY HIGHLIGHTS

Cheng says the comet is likely making its first visit to the inner solar system from the Oort cloud, a reservoir of hundreds of millions of comets encircling our solar system at a distance of about a light year.

FORBES: Budgets Nudge NASA Toward Balloon-Based Planetary Science: First Target? Comet ISON

Although solar panels will work on spacecraft at that distance, the desire for sufficient energy to drive many instruments means any mission would really need to go with radioisotope thermal generators (RTGs) - solid state electrical generators powered by the heat of radioactive decay.

BBC: NEWS | Science/Nature | Europe tells US: 'Come to Europa'

Now a Norwegian charity is running a pilot project to install 50 solar-powered street lights in the capital, while other donors are watching from a distance to see if that works.

ECONOMIST: Somalia