Astronomy Picture of the Day

Martian Polar Crater Ice Shifts with Seasonal Frost
Posted on: 31 Oct 2026

The planet Mars shares many landforms and weather patterns with the Earth, including changing seasons, volcanoes, canyons, dust storms and dust devils, and water ice. But one feature that Earth and Mars share among the eight planets in our solar system are polar ice caps. Both are one of each planet’s striking features, but the major difference is while Earth’s polar ice caps are both comprised of water, Mars’ north polar ice cap is only comprised of water while its southern polar ice cap is carbon dioxide. The reasons for this are determined by altitude, but Mars’ northern polar ice cap is one of the most studied regions primarily due to its water ice composition. But how does the north polar ice cap water ice change with the seasons compared to Earth, and what can this teach scientists about Mars’ climate history?

Ceres' Water Ice Can Mask Massive Surface Salt Deposits
Posted on: 31 Oct 2026

The dwarf planet Ceres is arguably one of the most overlooked and underappreciated planetary objects in the entire solar system. This could be because while Ceres has the same dwarf planet designation as Pluto, Ceres is largely considered an “asteroid” since it resides the in main asteroid belt. However, along with being the largest object in the main asteroid belt, Ceres’ mass comprises between 25 to 30 percent of all the mass of the entire main asteroid belt. Despite its lack of recognition, Ceres’ interior is layered like most rocky planets, including Pluto, and its surface displays evidence of past water ice activity (also called cryovolcanism) with several “bright spots”, which are highly reflective salt deposits. But what can these salt deposits teach scientists about Ceres’ formation and evolution?