2016: A year that unlocked mysteries of our solar system

Rather than acting as a barrier, Venus' clouds may offer insight into what lies beneath

From Mercury, the planet closest to the Sun, to the icy dwarf Pluto, scientists this year explored far reaches of our solar system, travelling unprecedented distances to make new discoveries and solve many mysteries of the vast space surrounding the Earth.

"This past year marked record-breaking progress in our exploration objectives," said Nasa Administrator Charles Bolden.

A newly discovered "great valley" in the southern hemisphere of Mercury provided more evidence that the small planet closest to the Sun is shrinking.

Scientists used stereo images from Nasa's MESSENGER spacecraft to create a high-resolution topographical map of Mercury that unveiled the broad valley - more than 1,000 kilometres long - extending into the Rembrandt basin, one of the largest and youngest impact basins on the innermost planet of our solar system.

About 400 kilometres wide and three kilometres deep, Mercury's great valley is larger than North America's Grand Canyon and wider and deeper than the Great Rift Valley in East Africa.

In July, scientists using observations from European Space Agency (ESA)'s Venus Express satellite, showed for the first time how weather patterns seen in the planet's thick cloud layers are directly linked to the topography of the surface below.

Rather than acting as a barrier to our observations, Venus' clouds may offer insight into what lies beneath.

Frozen beneath a region of cracked and pitted plains on Mars lies about as much water as what is in Lake Superior, largest of the Earth's Great Lakes, researchers using Nasa's Mars Reconnaissance Orbiter determined.

This reserve could prove to be a vital resource for astronauts in future manned-missions to the red planet.

"We advanced the capabilities we will need to travel farther into the solar system while increasing observations of our home and the universe, learning more about how to continuously live and work in space, and, of course, inspiring the next generation of leaders to take up our Journey to Mars and make their own discoveries," Bolden said.

Meanwhile, ESA's Schiaparelli - an entry, descent and landing demonstrator module launched in March - failed to successfully land on the surface of Mars. The ExoMars Trace Gas Orbiter (TGO) which carried the test lander continues to orbit the red planet.

The ExoMars programme will continue to investigate the Martian environment and findings may pave the way for a future Mars sample return mission in the 2020's.