Our world was rocked by last week’s announcement of good radar evidence for a liquid water “lake” under the Red Planet’s south pole. Senior Editor Emily Lakdawalla introduces us to the story that is then taken up by two of host Mat Kaplan’s favorite Martians. The Goddard Space Flight Center’s James Garvin headed NASA’s Mars exploration program, while NASA Ames astrobiologist Chris McKay co-founded the Mars Underground more than 35 years ago. Look up! Mars is still close by, and the Perseid meteor shower is around the corner. Bruce Betts gives us the What’s Up lowdown.
This beautiful image of Mars’ south pole was captured by the Mars Express orbiter in 2015. Now there’s good evidence for liquid water 1.5 kilometers below it.
ESA / Roscosmos / CaSSIS
ExoMars image of layered deposits at the south pole of Mars
The ExoMars Trace Gas Orbiter captured this view of part of the south polar ice cap on Mars on 13 May 2018. The poles of Mars have huge ice caps that are similar to Earth’s polar caps in Greenland and Antarctica. These caps are composed primarily of water ice and were deposited in layers that contain varying amounts of dust. They are referred to as the martian Polar Layered Deposits (PLD). Thanks to massive canyons that dissect the layered deposits, orbiting spacecraft can view the layered internal structure. The ExoMars orbiter’s Colour and Stereo Surface Imaging System, CaSSIS, viewed this 7 x 38 km segment of icy layered deposits near the margin of the South PLD, which extend as far north as 73ºS. Here, CaSSIS has imaged remnant deposits within a crater at this margin. The beautiful variations in color and brightness of the layers are visible through the camera’s color filters. It highlights the bright ice and the redder sandy deposits toward the top of the image.
ESA / NASA / JPL / ASI / Univ. Rome; R. Orosei et al 2018
Detecting buried water with radar
Radargram for MARSIS orbit 10737. A radargram is a bi-dimensional color-coded section made of a sequence of echoes in which the horizontal axis is the distance along the ground track of the spacecraft, the vertical axis represents the two-way travel time of the echo (from a reference altitude of 25 km above the reference datum), and brightness is a function of echo power. The continuous bright line in the topmost part of the radargram is the echo from the surface interface, whereas the bottom reflector at about 160 μs corresponds to the SPLD/basal material interface. Strong basal reflections can be seen at some locations, where the basal interface is also planar and parallel to the surface.