What can flying a kite over the Hawaiian islands tell us about past events that helped shape the landscape of Mars?
Quite a lot, apparently, according to scientist from the Lunar and Planetary Laboratory (LPL) at the University of Arizona.
Principal investigator Christopher Hamilton and his colleagues have used kites equipped with a suite of off-the-shelf instruments (including a camera and a GPS) and used them to study the lava that covers the Hawaiian landscape. Using parallel computing and powerful software algorithms, they then turn the images they collect into detailed 3D digital models of the terrain.
By comparing those models of Hawaii’s volcanic landscape to images of Mars captured using the HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter (MRO) spacecraft, the LPL team is hoping to find never-before seen details of the Red Planet’s surface. They will present their findings this week at the 46th Lunar and Planetary Science Conference in Texas.
“The idea is to understand places we can’t go by analyzing places we can go,” Hamilton, who joined the lab last year to form a terrestrial analog research group, said in a statement. “We can use geologically young and vegetation-free surface features here on Earth… as terrestrial analogs that can provide us with insights into processes that shape other planets.”
Studying the chemical desert
Hamilton studies volcanic surfaces on Mars to understand the thermal history of the Red Planet, in other words, how the planet’s internal processes manifest on the surface. Analyzing the lava flows of Hawaii enables the LPL team to “develop diagnostics that help us recognize the actual processes that led to the formation of a certain feature” on the Red Planet.
He and his colleagues selected Kilauea Volcano on the main island as their research target. The volcano is described as a “chemical desert” with several lava flows that are extremely young in a geological sense. When models of Kilauea are compared to images of the Martian surfaces taken using the HiRISE instrument, Hamilton explained that they found striking similarities.
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“We think this is how the big lava flows formed on Mars, which strongly suggests they may not be what they seem,” he explained. For instance, many of the features believed to be channels that were cut by running water in the past are more likely caused by volcanic processes.
More specifically, they were the result of a process known Hamilton refers to as fill-and-spill lava emplacement, during which lava accumulates like water in large perched ponds. Ultimately, the ponds are beached like a dam, causing in ‘catastrophic’ lava floods that create the channels.
“It is easy to draw conclusions based on our intuition of how water flows, so it is tempting to interpret similar features on Mars in the same way. But in fact these features formed by flowing lava, not water,” Hamilton explained, comparing the model to a 1974 lava flow at Kilauea.
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“We see that in certain areas, the surface is broken up into plates and what superficially looks like channels carved by running water. However, these turn out to be not carved at all, but rather are the result of a complex pattern of lava movements within the flow,” he said.
A volcanic bathtub ring
During the December 2014 event, liquid lava filled the area between cliffs like a giant bathtub, and when the perched lava pond breached, the lava began surging forward. This caused pieces of cooled surface lava to break apart, and fresh lava to well up from underneath. As the cool plates continued flowing towards the drain, the crumpled and left behind a “bathtub ring.”
“The question that drives us is, ‘How can we assemble this kind of data for Mars landscapes and decide whether a feature is volcanic or fluvial – shaped by water – and allow us to develop a story?’ ” said Hamilton. “A single surface texture doesn’t tell you anything if you can’t see the way in which the building blocks combine, such as the tiles that make up the pattern of a mosaic. The relationships between textures allow you where to look and what to look for.”
Modern day Ben Franklin
So he turned to Stephen Scheidt, a postdoctoral fellow at LPL who specializes in dune-building processes, to design and create the terrain-mapping kite system used in the study. The system featured a delta-wing kite outfitted with a camera. The kite was carefully flown over the region to produce images similar to aerial photographs taken from a airplane.
The kite collected one of these images, which are actually mosaics projected onto digital terrain models, every two seconds. Tens of thousands of images were captured at each location the kite flew over, and those pictures were then fed through computer software that removed distortions and stitched them together to create a virtual terrain model, Scheidt explained.
The process is known as orthorectification, and it requires both massive processing power and several weeks to render a terrain model. The result is a high-resolution model that Hamilton said can be used to “help us to decipher the geologic history of Earth and Mars.”