Planetary Picture of the Day
Week of April 14, 2025
Solely planetary bodies this week, working outward from Earth to Mars, Jupiter, and comet 67P/Churyumov–Gerasimenko.
Monday, 14 April 2025
Linear Sand Dunes
On March 25, 2013, an astronaut aboard the International Space Station took this photo of the Great Sandy Desert in northwest Australia, showcasing linear dunes separated in a roughly regular fashion. When you fly over such dune fields—either in an airplane or the space station—the fire scars stand out. Where thin vegetation has been burned, the dunes appear red from the underlying sand; dunes appear darker where the vegetation remains.
Strings of narrow lakes representing ancient rivers are also present in the region. The white feature down the center of the image is Lake Auld. The color results from a cemented combination of fine, clay-like sediment and salts from the evaporation of flood waters that occasionally fill the lake. Linear dunes can be seen entering Lake Auld on the east side. During flooding events, the sand of the dune noses is dispersed, becoming incorporated into the mud and salts of the lake floor sediments. During the long, intervening dry periods, sand can blow across the lake floor to build thinner, smaller dunes, visible as linear accumulations on the west side of the lake.
Tuesday, 15 April 2025
An Unusual Hole in Mars
What created this unusual hole in Mars? Actually, there are numerous holes pictured in this Swiss cheese-like landscape, with all but one of them showing a dusty, dark, Martian terrain beneath evaporating, light, carbon-dioxide ice. The most unusual hole is on the upper right, spans about 100 meters, and seems to punch through to a lower level. Why this hole exists and is surrounded by a circular crater remains a topic of speculation, although a leading hypothesis is that it was created by a meteor impact.
Holes such as this are of particular interest because they might be portals to lower levels that extend into expansive underground caves. If so, these naturally occurring tunnels are relatively protected from the harsh surface of Mars, making them relatively good candidates to contain Martian life. These pits are, therefore, prime targets for possible future spacecraft, robots, and even human interplanetary explorers.
Wednesday, 16 April 2025
By Jove!
Fantastically beautiful imagery of storms on Jupiter by NASA's Juno spacecraft, taken from 445 km above the gas giant's atmosphere on July 10, 2017. #JunoCam
Thursday, 17 April 2025
Cometary Close Up
Portrait of comet 67P/Churyumov–Gerasimenko in natural color. This image was taken with the OSIRIS NAC camera on ESA's Rosetta mission on 5 August 2014 from a range of 123 kilometers. Originating in the Kuiper Belt, 67P is a Jupiter-family comet with an orbital period of 6.45 years and will reach its next perihelion in 2028.
