The European Space Agency has released the early results from its Mars Express probe now orbiting the Red Planet.
The data include a batch of remarkable pictures taken at very high resolution.
The images show what appear to be sediments left in the bottoms of river-cut valleys, and details as fine as dust blowing over the rims of craters.
"This is no ordinary spacecraft," said David Southwood, Esa's head of science. "This is only the beginning. There is more to come in the next two years."
The science results were released at a news conference at Esa's Space Operations Centre in Darmstadt, Germany.
The event took place as the US space agency attempted to make full contact with its Spirit Mars rover, which has inexplicably stopped sending data back to Earth.
The European orbiter's instruments have also revealed new information about the stores of water-ice at the planet's south pole and the way it is mixed in with frozen carbon dioxide (CO2).
In addition, Esa scientists say they can see, for the very first time, water being lost from Mars' atmosphere.
But it is the images taken with the probe's High Resolution Stereo Camera that have generated the greatest excitement.
The camera can see details down to two metres and German researchers working on the mission have even constructed computer-generated movies from the pictures to show what it would be like to fly over the Red Planet in an aircraft.
The camera's lead scientist, Gerhard Neukum, from the Free University in Berlin, said Mars Express had already imaged nearly two million square kilometres of the Martian surface.
The area, covered at a resolution of 10 to 15 metres per pixel, was equivalent to the land coverage of France, Germany, Italy, Spain, Portugal and Austria combined, he said.
His team has already received more than 100 gigabytes of processed data - most of which has not even been looked at yet.
"We have done some instant science and I think we can firmly say 'yes, there was water acting on the surface of Mars'," Professor Neukum said.
His pictures show what appear to be sediments left in water-cut valleys and at the bottoms of craters which other instruments on the probe will now try to identify. There were also features that had been pictured that appeared to be evidence of glaciation, he added.
It is still very early in the two-year mission of Mars Express, but project scientists say they are thrilled with the initial returns of data they are getting from the spacecraft.
"We have already identified water vapour in the atmosphere and water-ice in the soil on the southern polar cap," said Vittorio Formisano, who looks after the probe's Planetary Fourier Spectrometer.
"We can identify water directly on the planet," added Jean-Pierre Bibring, from the Institute of Space Astrophysics, Orsay, France.
"It's mixed with CO2 essentially but if we go to areas which are a little warmer where there is no CO2, we have remaining water there."
At the end of the mission, he said, scientists should know the precise volume of water-ice still remaining on the planet's surface.
The US space agency's Mars Odyssey orbiter has already given a strong indication that there is water-ice on the southern pole. Its assessment comes from the use of a gamma ray spectrometer, which detects hydrogen, which with oxygen makes up water.
The Mars Express data amounts to a confirmation, because it arrives at the same conclusion but by a different technique: its Omega spectrometer analyses visible and infrared light rather than the gamma part of the energy spectrum.
Rickard Lundin, from the Swedish Institute of Space Science, is studying how the Sun is eroding the Martian atmosphere with an instrument called the Energetic Neutral Atoms Analyser.
"It shows us the 'planetary wind' which essentially describes water escape - but in an indirect way because what we see coming [off Mars] is oxygen and the oxygen is most likely coming from water."
Mars Express arrived at the Red Planet on 25 December. It operates from a polar orbit that takes it between 300 and 11,000 km from the planet's surface.
European scientists want the mission to:
At the heart of the mission is the desire to understand the history and current state of water on the planet which may say something about the presence of life - currently or in the far-distant past.
- map the mineral composition of the surface at 100-m resolution
- map the composition of the atmosphere and determine its global circulation
- determine the structure of the sub-surface to a depth of a few kilometres
- determine the effect of the atmosphere on the surface
- and determine the interaction of the atmosphere with the solar wind
So far, Mars Express has performed flawlessly. The one disappointment has been the loss of its lander probe, Beagle 2.
The British-built robot has not been heard from since it fell through the Martian atmosphere on Christmas Day.
All images are courtesy of the European Space Agency