Planetary Picture of the Day - Week of June 30, 2025

Monday, 30 June 2025

Rubin Observatory and Asteroids

Today is Asteroid Day, the anniversary of the Tunguska Event, when we raise awareness about potentially hazardous asteroids and their possible impacts on Earth. We also celebrate the addition of a new tool in our quest for planetary defense—the Vera Rubin Observatory. During the observatory's First Look last week, a new video revealed the discovery of over 2,100 new asteroids, including seven near-Earth objects (NEOs). This screenshot from the video shows a small portion of those discoveries, taken while looking at a small swath of the sky during this first image release.

Watch the full video: https://www.youtube.com/watch?v=DTuq-vBsDJE

Tuesday, 1 July 2025

Dark Sand Cascades on Mars

Naturally erupting dust streaks on Mars create structures that look surprisingly like trees near the planet's north pole. These streaks are dark basaltic sand pushed to the surface of sand dunes by sun-heated solid carbon dioxide ice, or dry ice, sublimating directly into vapor. The sand dunes form a nearly complete ring around Mars' north pole and are covered by a thin layer of reddish Martian dust and patches of dry ice.

Wednesday, 2 July 2025

The Cliffs of a Comet

Captured by the Rosetta spacecraft, this incredible image shows a one-kilometer-high cliff on Comet Churyumov–Gerasimenko, better known as 67P. The ragged cliff, as featured here, was imaged by Rosetta early in its mission. Because of the comet's low gravity, you could probably jump from the top of the cliff and fully enjoy the descent and the landing without too much trouble. A relatively smooth icy terrain is dotted with boulders as large as 20 meters across. Data from Rosetta indicates that the ice in 67P has a significantly different deuterium fraction -- and hence likely a different origin -- than the water in Earth's oceans.

Thursday, 3 July 2025

Dolmen of Guadalperal

The first two images here were taken by NASA/USGS Landsat satellites on July 24, 2013, and July 25, 2019. They show the Valdecañas Reservoir in western Spain before and during a European-wide drought that caused the shoreline to recede. The circle notes an area revealed during that drought, which contains a set of more than 100 standing granite stones dating back 7,000 years, seen up close in the final picture and known as the "Dolmen of Guadalperal".