Spidery shapes on Mars? Using a camera on a spacecraft that orbits the red planet, researchers have finally been able to track year-to-year changes of these enigmatic features – something they’ve been trying to capture for the past decade.
The spacecraft is NASA’s Mars Reconnaissance Orbiter (MRO). Using its High Resolution Imaging Science Experiment known as HiRISE, the orbiter captured the cumulative growth of these small spider-like features. This was the first time that the growth of the channels was observed from one spring to another.
Over the past three years, researchers have been able to see the growth of small trough features. Their growth is due to a process of thawing carbon dioxide that is thought to form the larger features as well, the “spiders.” The large features earned their nickname because of the numerous channels that usually converge at a central pit. The sizes of these spider features range from tens to hundreds of meters.
Through observing the active growth of the small troughs, researchers determine the average growth rate of the spiders. Based on this rate, more than a thousand years on Mars would be necessary! Each year on Mars is approximately 1.9 Earth years.
Sand dunes on Mars could be a contributing factor to the formation of miniature spiders. The dunes may also prevent the miniature spiders from becoming full-scale ones. Why? Moving sand – it may cover small spider formations.
During winter on Mars, sheets of carbon-dioxide ice or dry ice cover the ground near both the north and south poles of the planet. The spider-like features on the surface of Mars are found only in the south polar region. Mysterious dark fans on the surface are also found in these areas during spring every year.
In 2007, Hugh Kieffer of the Space Science Institute in Boulder explained that sunshine during the spring penetrates the ice which warms the ground underneath. This causes some of the carbon dioxide on the bottom of the ice sheet to thaw into gas. The now trapped gas builds up pressure until a crack is created in the carbon dioxide ice sheet. The trapped gas then erupts out of the ice sheet and during its travel toward the vent, picks up sand and dust particles that erode the ground. This also gives the geyser particles that fall back to Mars’ surface but downwind, creating dark spring fans.
Near the north pole of Mars six years ago, researchers found small channels near the dark spring fans which had been created by eruptions through dry ice. The small channels disappeared within a year.
Near the south pole, the troughs that were newly found occur at spring-fan sites. What makes them different than those near the north pole? Here, the troughs have remained and grown over three years. They resemble the spidery terrain through their pattern of branches.
The MRO spacecraft continues to teach us new things about the red planet. Following its two-year prime mission, NASA’s MRO is now in its fourth extension and investigating changes on the surface of Mars that occur seasonally and long-term. The spacecraft arrived at Mars in 2006.
Learn more about MRO at NASA.gov.