A cross-section of a thick sheet of underground ice is exposed at the steep slope (or scarp) that appears bright blue in this enhanced-color view from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter.


The history of Earth’s atmosphere is kept in libraries of rocks all over the world. For example, about 2.4 billion years ago, Earth developed layers of banded iron formations, donated to the archive by the Great Oxygenation Event. Rocks made of iron, silicon, and calcium compounds are durable, keeping records for billions of years. Another rock, ice, may not last as long as its harder cousins, but is excellent for keeping track of more recent atmospheric changes in much finer detail!

Recent images from NASA’s Mars Reconnaissance Orbiter (MRO) captured steep scarps that give a glimpse into Mars’s geologic past. Scarps, or escarpments, are areas where the geologic layers of a region become accessible at the surface either through erosion or tectonic activity. You can find examples in the San Francisco Bay Area, and many other places in the world.

In last week’s report, researchers discovered a layer of ice exposed in several areas of the martian surface. Prior missions, including the Mars Exploration Rovers, had already determined that Mars has stores of subsurface water. The discovery of exposed ice layers means that future manned missions may be able to acquire water simply by taking it from a hillside!

The exposed layers of ice also provide a means of investigating the recent history of Mars’ atmosphere. On Earth, climate scientists, including Nancy Bertler, study ice cores to learn about the atmosphere and geologic events that occurred as a glacier formed. As layers of snow compress to form a glacier, other material is sometimes trapped within the ice. For example, the ash released by volcanic eruptions settle around the whole planet. This layer of ash can be found in glaciers that formed when the eruption occurred, and gives us a record of geologic events.

In addition to particles of ash and dust, bubbles of air trapped within layers of snow can be trapped as the snow is compressed into ice. This means that we can directly measure the composition of the atmosphere a millions years in the past!

Using these techniques, we will be able to learn more about the geologic and atmospheric history of the Red Planet. This will include clues into mysteries such as when Mars’s surface water disappeared and what happened to its atmosphere.

You can learn more about ice core science conducted on Earth at the National Climatic Data Center’s website. More information on plans to send humans to explore Mars can be found on the NASA and SpaceX websites. To see a rock from Earth’s Moon, check out the display at the California Academy of Sciences, on the southern wall where planetarium tickets are distributed.


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