The dark side of Mars: Study reveals weathered glass deposits

April 26, 2012

New study reveals dark patches on Mars are weathered glass deposits

If you look at a map of Mars, you will see a mosaic of dark patches and lighter spots covering the planet. The various shades represent different sediments, but the exact composition of those sediments is something scientists are still trying to figure out. As a result of a study conducted by researchers at Arizona State University, scientists are one step closer to understanding the geology of the red planet. weathered glass Download Full Image

In a study published in the journal Geology, Jim Bell, School of Earth and Space Exploration (SESE) professor and Briony Horgan, SESE exploration postdoctoral fellow, report that the Martian northern lowlands are largely composed of chemically weathered glass.

Horgan and Bell began their research by collecting spectra data from the OMEGA imaging spectrometer on board the European Mars Express spacecraft. Because Mars Express is in an elliptical orbit, the spacecraft makes close passes over different areas of Mars, producing images from different times and elevations. The team used those images to produce a single map of the northern lowlands, and incorporated spectral data into that map. Translating spectral data, often represented in graphs, onto images made the spectra easier to analyze.

Once the team had the spectra mapped, they began to investigate the iron mineralogy of the sediments. The researchers found that the spectra they were observing had signatures that were consistent with a glass-rich composition.

“Glass is iron bearing, and it looks a lot like olivine and pyroxene, but it’s different enough that we can tell it apart,” explained Horgan. “When we started mapping this stuff out, we found that basically all of Acidalia Planitia, most of the north polar sand sea, and all of Utopia Planitia had that same glass signature. In total, that’s over ten million square kilometers of glassy surfaces.”

Based on lab studies, the team was able to determine that glass content of the sediments was approximately 80 to 90 percent.

“We hadn’t conclusively detected glass before on Mars,” said Horgan. “People had inferred that it must be there, since impacts and volcanoes create glass, but nobody had actually directly identified it before. So that begged the question – where did this stuff come from?”

Meteorite impacts can create glass, but usually not in the high concentrations that Horgan and Bell observed. Volcanoes, however, have the potential to create extremely large quantities of glass, especially explosive volcanoes that interact with ice and water.

Horgan and Bell used Iceland, a location where explosive volcanoes are common, as an analog to hypothesize about the conditions that could have produced the Martian glass they found.

Volcanoes in Iceland erupt underneath glaciers, and the interactions between water from the glaciers and lava from the volcanoes create incredibly explosive eruptions. The lava fragments, and transforms into particles of glass. Huge sand dunes and sand plain fields form that consist of 50 to 70 percent glass. Horgan and Bell hypothesize that the same process occurred during periods of volcanism on Mars.

This possibility presents an interesting new idea of Martian geologic history. Previously, mineral mapping evidence has been interpreted to indicate that most volcanism on Mars has been effusive (dominated by lava flows). These findings support the idea that explosive volcanism was also important in the planet's past, perhaps more important than previously thought.

Another intriguing finding is that the glass Horgan and Bell observed has been chemically weathered.

“When we see these glassy spectra, we also see a spectral signature that’s consistent with what happens when you expose glass to acid,” explained Horgan. “What that means is that these huge deposits are not only unique in that they indicate explosive volcanism, they also have experienced interactions with water.”

The northern lowlands were formed in the Amazonian epoch, the current and most recent geologic epoch on Mars. Scientists think of this epoch, which has lasted for approximately three billion years, as a very dry era, dominated by ice and snow. Horgan and Bell suggest that the chemical weathering observed on the glass is a result of melt from ice and snow during this epoch.

One question that begs further investigation is the exact nature of the glass deposits. Researchers are unsure of whether the northern lowlands are covered in a thick deposit of glass, or just a thin layer. The team also wants to see if sand dunes in other areas of Mars also exhibit these same glassy signatures. This could provide more support for the hypothesis of explosive volcanism on Mars.

Currently, the team at ASU is working on extending its map of Mars to cover the entire planet in order to explore some of the new avenues of research this study opens.

“The best you can do sometimes is to put these questions out there and intrigue your colleagues to get them to poke into it a little more,” said Bell. “And we’ll do some of that poking ourselves. There’s the whole rest of the planet to map.”

Written by Victoria Miluch

Nikki Cassis

marketing and communications director, School of Earth and Space Exploration

Water under the Sonoran summer sun

April 26, 2012

ASU’s new WEST program exposes students to water resource management in Sonora, Mexico

Hermosillo, the capital city of Mexico’s state of Sonora, is the largest city in the state, an important industrial hub, and the site of significant population growth in recent decades. It is also located in the middle of the Sonoran Desert, meaning that water supply is a constant concern. Recently, the state began building a 162-kilometer long aqueduct to bring more water to Hermosillo from the Yaqui River Basin, which also supplies agricultural users in Ciudad Obregon, sparking conflict between industrial water users in Hermosillo and agricultural users in Ciudad Obregon. Sonoran rain Download Full Image

Enrique Vivoni, ASU associate professor, and postdoctoral research associate Agustin Robles-Morua saw this situation as a perfect opportunity to expose students to current debates in water resource management. In the summer of 2012, six ASU undergraduates and four graduate students will join Vivoni and Robles-Morua in Sonora as a part of a month-long Water and Environmental Sustainability Training (WEST) research experience funded by the National Science Foundation’s International Research Experience for Students (IRES) program.

The WEST program consists of two weeks spent in Mexico sandwiched in between two weeks spent at ASU. In the program’s first week at ASU, students will learn about the geography of the region, read and discuss relevant papers, and help prepare instruments and sampling protocols they will use in Mexico.

Students will spend their first week in Mexico traveling between Hermosillo and Ciudad Obregon to meet with government officials and representatives of major water users in both regions and learn about different sides of the complex issue.

Robles-Morua emphasizes that the timing of the project is crucial. “We wanted to start this project at the same time this big infrastructure plan by the government of Sonora was going on so that we could be part of it.”

During its second week in Mexico, the group will travel north to the rural city of Rayón, where Vivoni has been leading an experimental watershed study, in collaboration with the University of Sonora and the Technical Institute of Sonora since 2004. The site has approximately 35 rain gauge and soil moisture stations, as well as two meteorological flux towers, that capture hydrologic data at a very high resolution. Students will learn how to use these instruments, analyze the data they collect, and participate in hydrologic experiments conducted at the sites.

A big part of the program is its collaboration with Mexican universities. ASU students will be working alongside Mexican students and faculty from Hermosillo’s University of Sonora and Ciudad Obregon’s Technical Institute of Sonora, who will be examining the same issues.

Upon their return to Arizona, ASU students will spend a week giving presentations summarizing their experiences.

Along with exposing students to water management issues and hydrologic experiments, WEST will also give ASU students a unique glimpse into the early stages of water infrastructure development and problems associated with water sustainability of desert regions.

“This is an area that’s currently developing its water infrastructure projects, and you don’t really see those projects being built in the US anymore because that occurred so many years ago,” says Robles-Morua. “Most of the projects in the US are now replacing old infrastructure, whereas in Mexico, this is like starting from zero. So this is another new experience they’ll get to see.”

This is the program’s inaugural year at ASU, and the project will extend into the next two summers of 2013 and 2014. Vivoni and Robles-Morua developed the program with their Mexican collaborators, using a similar effort Vivoni had led at the New Mexico Institute of Mining and Technology from 2006 to 2008 as a model.

The selected participants exemplify the multidisciplinary nature of the field of water resource management; students include ecologists, civil engineers, geologists, environmental engineers, and geography majors from a wide range of ASU departments and schools.

“Recently, water resource management has required a multidisciplinary approach to tackle a multidisciplinary problem,” say Robles-Morua. “We followed along on the same lines, having students from different perspectives that would provide us with different inputs during the course of the summer experience.”

Written by Victoria Miluch

Nikki Cassis

marketing and communications director, School of Earth and Space Exploration