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Over The Horizon

From Canterbury to Mars

Research carried out on the gravel bed rivers of the Canterbury Plains could provide useful analytical techniques to answer, comprehensively, a question that has intrigued people for generations: did water once flow on Mars?

Scientists at NIWA (the National Institute for Water and Atmospheric Research) have been taking a close look at the texture of gravel in Canterbury's rivers and related altimeter data, as part of their work in monitoring water flow.

"From this analysis we can determine the degree to which the surface texture has been worked' by water and the direction the water flowed," says Derek Goring of NIWA's Hydraulic Group. "It would be fascinating to see what this analysis gives us for Mars data."

In February, Goring visited the Astrogeology Division of the US Geological Survey in Flagstaff, Arizona, which has contracts with NASA to analyse data collected on various space missions. While there he picked up data from a preliminary digital terrain model derived from photos taken by the camera on Mars Pathfinder. The data covers an area 10 metres by 10 metres from the small spacecraft, and has a very high resolution of 1 millimetre vertically, taken at 1 centimetre horizontal intervals.

"We would like to subject these data to the same analysis as we carry out on altimeter data from gravel bed rivers in Canterbury," says Goring.

Pathfinder is sitting at the confluence of the Tiu and Ares Valles, near the huge canyon area of Valles Marineris. This vast canyon system stretching for over 4,000 kilometres, looks to have been caused by rifts in the Martian crust, but there is clear evidence in the area of landslides, wind and water erosion. There are also indications of ancient river channels and lakes.

At one point in Mars' history, known as the Hesperian Period, enormous outflow channels were carved with the release of tremendous floods of water that washed over the surface of the planet covering thousands of square kilometres.

As well as gathering data from the Pathfinder lander site, Goring has access to information captured by the Mars Orbiter Laser Altimeter (MOLA) orbiting above the planet. Several hundred passes over areas such as the enormous shield volcano of Olympus Mons have provided large amounts of data which can be analysed.

Olympus Mons rises to just over 26,000 metres, or three times the height of Mt Everest. A fractured lava field to the north of the old volcano has some intriguingly regular fissures and ridges, and is typical of deposits in the area. A new technique called wavelet analysis can be used to investigate this regularity.

"Wavelet analysis has been called a mathematical microscope," says Goring.

Such information could be used by geologists to investigate the properties of the lava flow, such as the molten rock's viscosity, temperature, cooling rate and so forth, Goring explains.

At the moment, however, any kind of international collaboration on this work is unlikely to happen due to a lack of funding for the analysis.

"The Americans have spent billions in securing the data which they just give away to scientists to analyse. We only need a few tens of thousands of dollars to do our analysis," says Goring.