Dark Side: Australian team maps Moon's hidden craters

Some 66 of the possible 280 additional craters on the Moon, in a photo from Western Australia's Curtin University in Perth released on June 18, 2013. 

Australian scientists Tuesday said they had identified a possible 280 additional craters on the Moon, a finding they said could shed light on the history of the Earth's natural satellite.

Australian scientists Tuesday said they had identified a possible 280 additional craters on the Moon, a finding they said could shed light on the history of the Earth's natural satellite.

By combining gravity and topography data collected by satellites, the scientists from Curtin University in Western Australia were able to use computer modelling to at first identify two basins on the far side of the Moon.

They later developed a high-resolution image to find a total of 280 "candidate basins" which they suspect are craters.

Will Featherstone

"There are many more (craters) that have been mapped from optical observations or from just the shape of the topography," researcher Will Featherstone told reporters.

"So there's many, many craters that were already known, we've just been able to apply this technique to enhance the ones that aren't so easy to see.

"What we have been able to use is the topography and the gravity together to get a stronger indication that there is something there that needs further investigation."

Featherstone said the researchers looked at the lunar surface on both the near and far sides of the Moon, the dark side being more challenging because satellites cannot be tracked from Earth when they are on that side.

To get around this, the researchers used data gathered from a mission which used multiple satellites which were tracking each other as they circled the Moon.

"So when the satellite orbiting the Moon went behind the far side and they couldn't be seen from Earth, they could be seen by other satellites," he said.

Featherstone said of the 280 possible craters, the researchers had classified 66 of them as distinctly visible according to both gravity and topography.

"Scientists can, instead of looking at every square inch of the Moon looking for basins, they can target these areas," he said.

"It just helps investigations of the Moon and the history of the Moon and the solar system," he added.

The team has also done some work on the gravity of Mars and Featherstone said other data sets were also available for Venus and other planets.

He said scientists were optimistic about further discoveries from applying their techniques to new gravity data from NASA's GRAIL mission, which ended in late 2012 when the two satellites - named Ebb and Flow - were deliberately crashed on the Moon.

NASA Cassini Describes first global topographic map of Titan

These polar maps show the first global, topographic mapping of Saturn's moon Titan, using data from NASA's Cassini mission. 

To create these maps, scientists employed a mathematical process called splining, which uses smooth curved surfaces to "join" the areas between grids of existing topography profiles obtained by Cassini's radar instrument.

Image credit: NASA/JPL-Caltech/ASI/JHUAPL/Cornell/Weizmann

Scientists have created the first global topographic map of Saturn's moon Titan, giving researchers a valuable tool for learning more about one of the most Earth-like and interesting worlds in the solar system.

The map was just published as part of a paper in the journal Icarus.

Titan is Saturn's largest moon - at 1,600 miles (2,574 kilometers) across it's bigger than planet Mercury - and is the second-largest moon in the solar system.

Scientists have an affinity with Titan because it's the only moon in the solar system known to have clouds, surface liquids and a mysterious, thick atmosphere.

The cold atmosphere is mostly nitrogen, like Earth's, but the organic compound methane on Titan acts the way water vapor does on Earth, forming clouds and falling as rain and carving the surface with rivers.

Organic chemicals, derived from methane, are present in Titan's atmosphere, lakes and rivers and may offer clues about the origins of life.

Ralph Lorenz

"Titan has so much interesting activity - like flowing liquids and moving sand dunes - but to understand these processes it's useful to know how the terrain slopes," said Ralph Lorenz, a member of the Cassini radar team based at the Johns Hopkins University Applied Physics Laboratory, Laurel, Md., who led the map-design team.

"It's especially helpful to those studying hydrology and modeling Titan's climate and weather, who need to know whether there is high ground or low ground driving their models."

Titan's thick haze scatters light in ways that make it very hard for remote cameras to "see" landscape shapes and shadows, the usual approach to measuring topography on planetary bodies.

Virtually all the data we have on Titan comes from NASA's Saturn-orbiting Cassini spacecraft, which has flown past the moon nearly 100 times over the past decade.

On many of those flybys, Cassini has used a radar imager, which can peer through the haze, and the radar data can be used to estimate the surface height.

To create the first global, topographic map of Saturn's moon Titan, scientists analyzed data from NASA's Cassini spacecraft and a mathematical process called splining. 

This method effectively uses smooth curved surfaces to "join" the areas between grids of existing topography profiles obtained by Cassini's radar instrument. 

In the upper panel of this graphic, gold colours show where radar images have been obtained over almost half of Titan's surface. 

Image credit: NASA /JPL-Caltech /ASI /JHUAPL /Cornell/Weizmann

Steve Wall

"With this new topographic map, one of the most fascinating and dynamic worlds in our solar system now pops out in 3-D," said Steve Wall, the deputy team lead of Cassini's radar team, based at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

"On Earth, rivers, volcanoes and even weather are closely related to heights of surfaces - we're now eager to see what we can learn from them on Titan."

There are challenges, however. "Cassini isn't orbiting Titan," Lorenz said.

"We have only imaged about half of Titan's surface, and multiple 'looks' or special observations are needed to estimate the surface heights. If you divided Titan into 1-degree by 1-degree [latitude and longitude] squares, only 11 percent of those squares have topography data in them."

Lorenz's team used a mathematical process called splining - effectively using smooth, curved surfaces to "join" the areas between grids of existing data.

"You can take a spot where there is no data, look how close it is to the nearest data, and use various approaches of averaging and estimating to calculate your best guess," he said.

"If you pick a point, and all the nearby points are high altitude, you'd need a special reason for thinking that point would be lower. We're mathematically papering over the gaps in our coverage."

More information: 
The map, as well as a paper on the project ("A Global Topography Map of Titan"), appear in the journal Icarus and are available online at: www.sciencedirect.com/science/article/pii/S0019103513001620