planetary geology

Graduate student Debra Hurwitz and the object of her study: Venus has a lot to teach us about the solar system.

Credit: John Abromowski / Brown University

Graduate student maps Venus’s north pole

Debra Hurwitz’s map will shed new light on a planet that has been largely ignored by planetary scientists in favor of the moon and Mars.

By Richard C. Lewis  |  December 20, 2009  |  Email to a friend

When Debra Hurwitz arrived as a graduate student at Brown in fall 2007, she had a project waiting for her. Her advisor, James “Jim” Head III ’69 Ph.D., was working with the U.S. Geological Survey (USGS) to map sections of Venus. Hurwitz had helped with some mapping of Venus as an undergraduate at Pomona College, but now she was challenged to map an area by herself.

“It was basically me starting from scratch, from the very beginning,” she said.

Two years later, Hurwitz has created the first publishable map of Venus’s north pole. The map has been sent to the USGS to review and is expected to be accepted as the most comprehensive topographical survey of the polar region of Earth’s sister planet. Hurwitz’s map and others in progress are expected to shed new light on a planet that mostly has been ignored in the space community in favor of bodies such as the moon and Mars.

Hurwitz believes Venus has a lot to teach us about the solar system and our home planet. While Mars gets more attention due to its watery past and its potential to have hosted life, the red planet is about half the size of Earth and has been relatively static and lifeless for likely the last few billion years.

“But Venus is very similar in size to the Earth,” Hurwitz, a 24-year-old from Houston, explains, “so it’s very possible it had a similar evolution and may be a volcanically active planet today.”

Hurwitz’s map reveals most of Venus’s north pole, save for two areas in which the orbiting spacecraft failed to capture enough data to determine surface features. Scientists can pick out mountain belts some 21,000 feet above mean planetary radius, ridges, low-lying volcanic plains, and other significant features on the landscape.

Hurwitz’s map of the north pole of Venus.: Hurwitz’s map of the north pole of Venus. Head said Venus’s north pole is important because the region is a “confluence of all different sorts of terrains” that can help scientists unravel how the planet evolved. For example, geologists think that Venus is a single-plate planet, meaning it doesn’t have a crust that’s been broken up through plate tectonics, the sliding and collision of plates on Earth that produce earthquakes, volcanoes and mountains – although the single-plate idea hasn’t been universally accepted.

To produce the map, Hurwitz worked with data obtained by the NASA spacecraft Magellan when it orbited Venus from 1990 to 1994. The spacecraft’s research team didn’t dare take measurements near Venus’s hot, intensely pressurized atmosphere, instead opting for a highly elliptical orbit in which Magellan bounced radio waves off the surface from 182 miles to as far away as 5,296 miles away. The mission yielded data that were quite coarse, especially by current space exploration standards. Magellan produced images that are at best 75-meter spatial resolution, meaning each pixel covers 75 meters of the surface; by contrast, the HiRISE instrument aboard the still-orbiting spacecraft Mars Reconnaissance Orbiter returns images at one-meter spatial resolution. Put another way, HiRISE can see a table on the Martian surface, while Magellan would be hard-pressed to identify a building stretching a city block on Venus.

Even more limiting, the images yield about 80 meters in vertical resolution, Hurwitz says, meaning the instruments would fail to detect any topographical feature less than 80 meters in height.

Despite those constraints, her map lets planetary geologists expand the debate over Venus’s origin, evolution, and geology today. Ideally, another mission would be able to zoom in closer and obtain higher-resolution data.

“There’s so much to do, and I’d love to get another mission there,” Hurwitz says.