Planetary Picture of the Day
Week of February 17, 2025
This week's collection includes everything melting, flowing, and/or exploding, from thawing gullies on Mars to volcanoes on the moon and Earth to a supernova remnant in the Large Magellanic Cloud.
Monday, 17 February 2025
Dusty Water Ice in Mars' Terra Sirenum
This image from NASA's Mars Reconnaissance Orbiter (MRO) shows white material believed to be dusty water ice lining the edges of Martian gullies in a region named Terra Sirenum. Scientists believe dust particles within this ice act similarly to dust that falls onto glaciers on Earth, warming up in sunlight and causing subsurface pockets of meltwater to form.
On Earth, the dust that builds up on glaciers is called cryoconite, and the pockets it forms are called cryoconite holes. These pockets of water on our planet are often teeming with simple life, including algae, fungi, and cyanobacteria. Scientists believe similar shallow pools of water could exist on Mars, and may also be excellent places to search for life on the Red Planet today.
This enhanced-color image was captured by MRO's HiRISE (High-Resolution Imaging Science Experiment) camera on Dec. 25, 2016.
The blue color at the bottom of the gullies is likely coarse sand (not ice); the hue would not be perceptible to the human eye. However, HiRISE can detect this color by looking at the scene in far-infrared wavelengths.
Tuesday, 18 February 2025
Charco de los Clicos
Timanfaya National Park is a Spanish national park in the southwestern part of Lanzarote, in the Canary Islands. It covers parts of the municipalities of Tinajo and Yaiza. On the west coast of the island, an almost otherworldly landscape exists. Here, the crater of an extinct volcano submerges into the Atlantic Ocean, forming a lagoon known as the Charco de los Clicos (Green Lagoon). The lagoon's green color is caused by algae at the bottom.
Wednesday, 19 February 2025
Three Planets at HR8799
This image shows the light from three planets orbiting a star 120 light-years away. The planets' star, called HR8799, is located at the spot marked with an "X." This picture was taken using a small, 1.5-meter portion of the Palomar Observatory's Hale Telescope, north of San Diego, California. This was the first time a picture of planets beyond our solar system had been captured using a telescope with a modest-sized mirror -- previous images were taken using larger telescopes. The three planets, called HR8799b, c, and d, are thought to be gas giants like Jupiter, but more massive. They orbit their host star at roughly 24, 38, and 68 times the distance between our Earth and the sun, respectively (Jupiter resides at about 5 times the Earth-sun distance).
Thursday, 20 February 2025
Young Volcanism?
One of the early findings from NASA's Lunar Reconnaissance Orbiter was the discovery of features known as Irregular Mare Patches (IMPs) scattered across the near side of the moon. These landforms are generally considered volcanic. However, their ages are hotly debated. They may be as young as 50 million years or as old as 3.5 billion years. The Aristarchus IMP (25.045°N, 313.233°E) is one of the smallest and most enigmatic IMPs. The fact that this IMP is found within the Aristarchus crater ejecta suggests it formed after the crater, which is dated at 200 million years.
Alternatively, this IMP may have formed as part of ejecta emplacement from the Aristarchus crater forming impact. However, no other crater ejecta on the Moon exhibits a similar landform.
Friday, 21 February 2025
Heart and Soul
Located 168,000 light-years away in the Large Magellanic Cloud, Supernova (SN) 1987A has been a target of intense observations at wavelengths ranging from gamma rays to radio for nearly 40 years, since its discovery in February of 1987. Recent observations by Webb’s NIRCam (Near-Infrared Camera) provide a crucial clue to our understanding of how a supernova develops over time to shape its remnant.
This image reveals a central structure like a keyhole. This center is packed with clumpy gas and dust ejected by the supernova explosion. The dust is so dense that even near-infrared light that Webb detects can’t penetrate it, shaping the dark “hole” in the keyhole. A bright, equatorial ring surrounds the inner keyhole, forming a band around the waist that connects two faint arms of hourglass-shaped outer rings. The equatorial ring, formed from material ejected tens of thousands of years before the supernova explosion, contains bright hot spots, which appeared as the supernova’s shock wave hit the ring. Now spots are found even exterior to the ring, with diffuse emission surrounding it. These are the locations of supernova shocks hitting more exterior material.
In this image, blue represents the light at 1.5 microns (F150W), cyan at 1.64 and 2.0 microns (F164N, F200W), yellow at 3.23 microns (F323N), orange at 4.05 microns (F405N), and red 4.44 microns (F444W).
