Space and astronomy news
We can thank NASA’s New Horizons spacecraft for opening our eyes up to Pluto’s complexity. On July 14th, 2015, the spacecraft came within 12,500 km (7,800 mi) of the dwarf planet. During the flyby, New Horizons was able to characterize Pluto’s atmosphere and its surface.
Among the things New Horizons saw was a region of snowcapped mountains.
Continue reading “Pluto has Snowcapped Mountains, But Why?”
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Views from the window of NASA’s DC-8 reveal sweeping expanses of ice and rock as part of the ongoing 2011 Operation IceBridge survey of Antarctica’s ice cover.
Now in its third season, Operation IceBridge is a six-year-long mission to study the dynamics of the Antarctic and Arctic ice sheets. It’s the largest ever aerial survey of the polar ice and will yield valuable data on the state of Earth’s vast reservoirs of frozen water, including the land and sea underneath and how they are being affected by today’s rapidly changing climate.
Researchers – like Michael Studinger, who took the incredible photos seen here – fly over Greenland during the months of March through May and over Antarctica in October and November. NASA’s instrument-laden DC-8 flies over these remote locations at a low altitude of about 1,500 feet, often with little or no advance weather data.
98 percent of Antarctica is covered with ice. Information obtained by Operation IceBridge will be combined with satellite data to create the most accurate models possible of Antarctic ice loss and how it will affect future sea level rise.
This season’s Antarctic IceBridge campaign features NASA’s DC-8, at 157 feet long the largest plane in the agency’s airborne research fleet, and will also feature the debut of the Gulfstream V (G-V) operated by the National Science Foundation and National Center for Atmospheric Research.
While the DC-8 flies at low altitudes, the G-V will fly above 30,000 feet to utilize its Land, Vegetation and Ice Sensor (LVIS), which makes detailed topographic studies of the surface.
“With IceBridge, our aim is to understand what the world’s major ice sheets could contribute to sea-level rise. To understand that you have to record how ice sheets and glaciers are changing over time.”
– Michael Studinger, IceBridge project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md.
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There are many ways rocks can be textured. Wind erosion, water erosion, the escape of volcanic gases during their formation (in the case of igneous rocks)… all these forces can create the pitted textures found on many rocks on Earth… and perhaps even on Mars. And according to a report published by a group of planetary geologists led by James Head of Rhode Island’s Brown University, another method may also be at play on Mars: melting snow.
Here on Earth in the hyper-arid dry valleys of Antarctica, water from melting snow erodes the surfaces of dark boulders, creating pitted textures similar to what has been found at many locations on Mars.
In order for that process to be truly analogous, though, a few conditions would have to be met on the red planet. First, the atmospheric pressure must be high enough to allow water to remain – if only temporarily – in a liquid state. Water that instantly boils away won’t have enough time to chemically attack the rock. Second, the rock itself must be at least warm enough to not freeze the water (again, must be liquid.) And third, there must actually be water, snow or frost present.
While one or more of these factors may be currently present in locations on Mars, they have not yet been found to exist all together in the same place. But that’s just what’s been found now… in Mars’ geologic past these may all have very well existed either in isolated locations or perhaps even planet-wide.
The paper’s abstract states:
For example, increases in atmospheric water vapor content (due, for example, to the loss of the south perennial polar CO2 cap) could favor the deposition of snow, which if collected on rocks heated to above the melting temperature during favorable conditions (e.g., perihelion), could cause melting and the type of locally enhanced chemical weathering that can cause pits.
In other words, if the dry ice at Mars’ south pole had melted at one point, freed-up water vapor could have fallen on rocks elsewhere as snow. If Mars were at a point in its orbit closest to the Sun and therefore experiencing warmer temperatures the snow could have then melted – especially upon darker rock surfaces.
Still, it’s possible – or even probable – that the weathering did not occur at a consistent rate across the entire surface of the rocks. Some sides may have weathered faster or slower than others, depending on how they were exposed to the elements. But if there’s one thing Mars has had a surplus of, it’s time. Even if the processes outlined in the report are indeed the cause of Mars’ pitted rocks, they have likely been in play over many hundreds of millions – even billions – of years.
Read the team’s report on the Journal of Geophysical Research here.
Thanks to Stu Atkinson for his color work on the images from Opportunity. Check out his blog The Road to Endeavour for updates on the rover’s progress.
Have you ever noticed how the snow packs on a car windshield after a heavy snowfall? While the temperature is cold, the snow sticks to the surface and doesn’t slide off. After temperatures warm up a little, however, the snow will slide down the front of the windshield, often in small slabs. This is an avalanche on a miniature scale.
On the other hand, a mountain avalanche in North America might release 229,365 cubic meters (300,000 cubic yards) of snow. That’s the equivalent of 20 football fields filled 10 feet deep with snow. However, such large avalanches are often naturally released. They are primarily composed of flowing snow but given their power, they are also capable of carrying rocks, trees, and other forms of debris with them.
In mountainous terrain avalanches are among the most serious objective hazards to life and property, with their destructive capability resulting from their potential to carry an enormous mass of snow rapidly over large distances.
Avalanches are classified based on their form and structure, which are also known as “morphological characteristics”. Some of the characteristics include the type of snow involved, the nature of what caused the structural failure, the sliding surface, the propagation mechanism of the failure, the trigger of the avalanche, the slope angle, direction, and elevation.
All avalanches are rated by either their destructive potential or the mass they carry. While this varies depending on the geographical region – – all share certain common characteristics, ranging from small slides (or sluffs) that pose a low risk to massive slides that come that pose a significant risk.
An avalanche has three main parts: the starting zone, the avalanche track, and the runout zone. The starting zone is the most volatile area of a slope, where unstable snow can fracture from the surrounding snowcover and begin to slide. The avalanche track is the path or channel that an avalanche follows as it goes downhill. The runout zone is where the snow and debris finally come to a stop.
Several factors may affect the likelihood of an avalanche, including weather, temperature, slope steepness, slope orientation (whether the slope is facing north or south), wind direction, terrain, vegetation, and general snowpack conditions. However, weather remains the most likely factor in triggering an avalanche.
During the day, as temperatures increase in a mountainous region, the likelihood of an avalanche increases. Regardless of the time of year, an avalanches will only occur when the stress on the snow exceeds the strength either within the snow itself or at the contact point where the snow pack meets the ground or the rock surface.
Although avalanches can occur on any slope given the right conditions, in North America certain times of the year and certain locations are naturally more dangerous than others. Wintertime, particularly from December to April, is when most avalanches will occur with the highest number of fatalities occurs in January, February and March, when the snowfall amounts are highest in most mountain areas.
In the United States, 514 avalanche fatalities have been reported in 15 states from 1950 to 1997. In the 2002–2003 season there were 54 recorded incidents in North America involving 151 people.
In Canada’s mountainous province of British Columbia, a total of 192 avalanche-related deaths were reported between January 1st, 1996 and March 17th, 2014 – an average of roughly ten deaths per year. During the winter of 2014, avalanche concerns also forced the closure of the Trans-Canada highway on a number of occasions.
Not too surprisingly, Earth is not the only planet in the Solar System to experience avalanches. Wherever their is mountainous terrain and water ice, which is not uncommon, there is the likelihood that material will come loose and cause a cascading slide to take place.
On February 19th, 2008, NASA’s Mars Reconnaissance Orbiter captured the first ever image of active avalanches taking place the Red Planet. The avalanche occurred near the north pole, where water ice exists in abundance, and was captured by the MRO’s HiRISE (High Resolution Imaging Experiment) camera completely by accident.
The images showed material – likely to include fine-grained ice dust and possibly large blocks – detaching from a towering cliff and cascading to the gentler slops below. The occurrence of the avalanches was spectacularly revealed by the accompanying clouds of fine material (visible in the photographs) that continue to settle out of the air.
The largest cloud (shown in the upper images) was about 180 meters (590 feet) across and extended about 190 meters (625 feet) from the base of the steep cliff. Shadows to the lower left of each cloud illustrate further that these are three dimensional features hanging in the air in front of the cliff face, and not markings on the ground.
The photo was unprecedented because it allowed NASA scientists to get a glimpse of a dramatic change on the Martian surface while it was happening. Despite seeing countless pictures that have detailed the planet’s geological features, most appear to have remained unchanged for several million years. It also showed that terrestrial events like avalanches are not confined to planet Earth.
We have written many articles about the avalanche for Universe Today. Here’s an article about the Mars avalanche predicted by geologists, and here’s an article about the volcanic tuff.
If you’d like more info on avalanche, check out NASA Science News: Avalanche on Mars. And here’s a link to the American Avalanche Association Homepage.
We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.
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