Planetary Radio • Dec 27, 2017

Flowing Water on Mars? Not So Much

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20171227 colin dundas thumbnail

Colin Dundas

Planetary Geologist for U.S. Geological Survey

Mars scientists dubbed them recurring slope lineae or RSLs. They sure looked like evidence of liquid water flowing down hillsides and ridges on the Red Planet. New research led by US Geological Survey Planetary Geologist Colin Dundas says they are probably no more than dry sand and dust. Emily Lakdawalla reports that NASA has narrowed the choices for the next New Frontiers mission to a Titan or a comet lander. And it’s time for the last 2017 What’s Up look around the night sky by Bruce Betts.

Recurring slope lineae in Newton Crater, Mars
Recurring slope lineae in Newton Crater, Mars This image from NASA's Mars Reconnaissance Orbiter show recurring slope lineae — narrow (0.5 to 5 meters, or 1.6 to 16 feet wide), relatively dark-toned features that form on steep (25-40˚), southern-hemisphere slopes, and that appear in early spring. They grow longer in the downslope direction during spring and summer, and fade during autumn and winter.Image: NASA / JPL / UA / Emily Lakdawalla

This week's question:

What was the last successful Soviet mission to the Moon?

To submit your answer:

Complete the contest entry form at or write to us at [email protected] no later than Wednesday, January 3rd at 8am Pacific Time. Be sure to include your name and mailing address.

Last week's question:

What two orbiters are part of the European Space Agency’s BepiColombo mission to Mercury?


The answer will be revealed next week.

Question from the week before:

“Cometroid” (not at all an official IAU classification) 3200 Phaeton is responsible for the annual Geminids meteor shower. Who was the mythical Phaeton’s father?


Helios the sun god was Phaethon’s dad in Greek mythology. This got asteroid 3200 Phaethon named after the kid.