New data collected by NASA's Voyager 1 spacecraft have helped scientists confirm that the far-flung probe is indeed cruising through interstellar space, the researchers say. Voyager 1 made headlines around the world last year when mission scientists announced that the probe had apparently left the heliosphere — the huge bubble of charged particles and magnetic fields surrounding the sun — in August 2012.

They came to this conclusion after analyzing measurements Voyager 1 made in the wake of a powerful solar eruption known as a coronal mass ejection, or CME. The shock wave from this CME caused the particles around Voyager 1 to vibrate substantially, allowing mission scientists to calculate the density of the probe's surroundings (because denser plasma oscillates faster.)

The robots, known as Spheres (Synchronised Position Hold, Engage, Reorient, Experimental satellites), currently have limited capabilities.

It is hoped the smartphones, powered by Google's Project Tango, will equip the robots with more functionality.

The robots have been described by experts as "incredibly clever".

When Nasa's robots first arrived at the International Space Station in 2006, they were only capable of precise movements using small jets of CO2, which propelled the devices forwards at around an inch per second.

"We wanted to add communication, a camera, increase the processing capability, accelerometers and other sensors," Spheres project manager Chris Provencher told Reuters.

The wingspan of Pelagornis sandersi dwarfs that of today's biggest flier, the royal albatross, whose span measures a "mere" 11.5 feet (3.5 meters). And it rivals that of the largest flying bird on record: Argentavis magnificens—a South American condor with a 23-foot (7-meter) wingspan that glided among the mountaintops of the Andes six million years ago.

"Pelagornis was certainly much lighter and a better 'flier'" than the vanished giant condor, says paleontologist Antoine Louchart of France's Institute of Functional Genomics in Lyon, who was not involved with the study.