Tell-tale Evidence of Bouncing Boulders on Mars

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What are the types of things that happen on Mars when we're not looking? Some things we'll never know, but scientists with the HiRISE camera on the Mars Reconnaissance Orbiter have seen evidence of bouncing boulders. They haven't actually captured boulders in the act of rolling and bouncing down the steep slope of an impact crater (but they have

captured avalanches

while they were happening!)

Instead, they see distinctive bright lines and spots on the side of a crater, and these patterns weren't there the last time HiRISE imaged this crater 5 years ago (2.6 Mars years ago), in March 2008.

"The discontinuous bright spots indicate bouncing, so we interpret these features as due to boulders bouncing and rolling down the slope," said HiRISE principal investigator Alfred McEwen, writing on the

HiRISE website.

Where did the boulders come from?

"Maybe they fell off of the steep upper cliffs of the crater, although we don't see any new bright features there that point to the source," McEwen said. "Maybe the rocks were ejecta from a new impact event somewhere nearby."

The trails are quite bright, and McEwen said that perhaps the shallow subsurface soil here is generally brighter than the surface soil, just like part of Gusev Crater, as the Spirit rover found. McEwen added that the brightness can't be from ice because this is a warm equator-facing slope seen in the summer.

Source:

HiRISE

Nancy Atkinson

Nancy Atkinson

Nancy Atkinson is a space journalist and author with a passion for telling the stories of people involved in space exploration and astronomy. She is currently retired from daily writing, but worked at Universe Today for 20 years as a writer and editor. She also contributed articles to The Planetary Society, Ad Astra (National Space Society), New Scientist and many other online outlets.

Her 2019 book, "Eight Years to the Moon: The History of the Apollo Missions,” shares the untold stories of engineers and scientists who worked behind the scenes to make the Apollo program so successful, despite the daunting odds against it. Her first book “Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos” (2016) tells the stories of 37 scientists and engineers that work on several current NASA robotic missions to explore the solar system and beyond.

Nancy is also a NASA/JPL Solar System Ambassador, and through this program, she has the opportunity to share her passion of space and astronomy with children and adults through presentations and programs. Nancy's personal website is nancyatkinson.com