APOD Log

2026 July 21

Turtle Rock on Mars Image Credit: NASA/JPL-Caltech/MSSS; Processing & License: Thomas Thomopoulos

Explanation: Is this a fossilized turtle on Mars? No. Although resembling a large Earth tortoise, this is a layered rock outcrop on Mars that is estimated to span about 15 meters, making it much larger than turtles on Earth. NASA’s robotic Curiosity rover came across this unusual mound, dubbed Miraflores, last month during its 4922nd Martian day exploring Mars. The small butte may survive because it was somehow more resistant to erosion than surrounding rock. More recent wind has now covered its top with orange Martian sand. Below the top shell, many layers of stratified rock are visible, possibly indicating a long history of intermittent wind-blown sand being deposited and then hardened by ground water. Similar wind-eroded layered landforms, such as yardangs in the Qaidam Desert of China, exist here on Earth. Curiosity and its companion rover Perseverance continue to investigate the ancient history of Mars as well as searching for signs of primeval life.

2026 July 20

NGC 3576: The Statue of Liberty Nebula Image Credit & Copyright: Logan Carpenter

Explanation: What's happening in the Statue of Liberty nebula? Bright stars and interesting molecules are forming and being liberated. The complex nebula resides in the star forming region called RCW 57, and besides the iconic monument, to some looks like a flying superhero or a weeping angel. This re-assigned color image showcases dense knots of dark interstellar dust, fields of glowing hydrogen gas ionized by these stars, and great loops of gas expelled by dying stars. A detailed study of NGC 3576, also known as NGC 3582 and NGC 3584, uncovered at least 33 massive stars in the end stages of formation, and the clear presence of the complex carbon molecules known as polycyclic aromatic hydrocarbons (PAHs). PAHs are thought to be created in the cooling gas of star forming regions, and their development in the Sun's formation nebula five billion years ago may have been an important step in the development of life on Earth.

2026 July 19

Flying Saucer Crash Lands in Utah Desert Image Credit: USAF 388th Range Sqd., Genesis Mission, NASA

Explanation: A flying saucer from outer space crash-landed in the Utah desert after being tracked by radar and chased by helicopters. The year was 2004, and no space aliens were involved. The saucer, pictured here, was the Genesis sample return capsule, part of a human-made robot Genesis spaceship launched in 2001 by NASA itself to study the Sun. The unexpectedly hard landing at over 300 kilometers per hour occurred because the parachutes did not open as planned. The Genesis mission had been orbiting the Sun collecting solar wind particles that are usually deflected away by Earth's magnetic field. Despite the crash landing, many return samples remained in good enough condition to analyze. Genesis-related discoveries included new details about the composition of the Sun and how the abundance of some types of elements differ across the Solar System. These results have provided intriguing clues into details of how the Sun and planets formed billions of years ago.

2026 July 18

Shadow and Rainbow Image Credit & License: Dave Loschiavo

Explanation: At sunset, an alignment of rainbow and mountain shadow was captured in this remarkable snapshot. The stunning view was recorded from a fire lookout on Smith Peak in the Plumas National Forest near Portola, California on July 13. Still, near sunset it's no accident that the majestic mountain shadow seems to point to the center of the graceful rainbow arc. Due to perspective and the long line of sight the mountain shadow naturally forms a tapering triangular shape, its apex positioned at the point opposite the Sun on the horizon. Following thunderstorms across the region, the rainbow arcs across the early evening sky, with its colorful and characteristic 42 degree arc formed as sunlight is refracted and reflected by the atmospheric water droplets. The geometric center of a rainbow arc lies at the antisolar point. And in this scene from the golden hour on planet Earth, that's also oposite the setting Sun along the distant horizon.

2026 July 17

The Dust Trail of Comet Tempel 2 Image Credit & Copyright: Dan Bartlett

Explanation: Comet 10P/Tempel 2 orbits the Sun once every 5.4 years. Currently visible in binoculars or small telescopes toward the constellation Capricornus, the periodic comet is captured in this sharp telescopic image from July 11 sporting a bright nuclear region and pretty greenish coma. Remarkably, a thin dust trail, not a typical dust tail, is also seen extending both east and west of the Tempel 2 nucleus. Unlike a comet dust tail, which tends to temporarily fan out in a direction away from the Sun, this dust trail is due to the residual dust shed during many past orbits along this ancient periodic comet's orbital plane. In fact, Tempel 2's dust trail may get a little narrower and brighter from our perspective as Earth crosses through the comet's orbital plane on July 20. Comet 10P/Tempel 2 will reach a perihelion on August 2, and make its closest approach to Earth on August 3.

2026 July 16

NGC 300: A Cosmic Gemstone with Stars and Gas Clouds Image Credit & Copyright: Team Ciel Austral Text: Cecilia Chirenti (NASA GSFC, UMCP, CRESST II)

Explanation: This sparkling, colorful gemstone is a spiral galaxy, NGC 300. It is one of the closest spiral galaxies to Earth, only about 6 million light-years away. But does it really look like this? Here is a more standard portrait of it. This unusual image combines the light from the stars and dust within the galaxy with the light from ionized clouds of interstellar gas shown in red (Sulphur), green (Hydrogen) and blue (Oxygen). Combining red and green light in different proportions makes yellow or orange light, most visible in the image. Light from other ionized gases is also at work in neon signs, fluorescent tubes and street lights. These massive clouds of ionized gas are typically created by young, massive stars that produce high-energy ultraviolet radiation capable of ionizing the gas. Massive stars are short-lived, compared with lighter stars like our sun, and explode as supernovas at the end of their lives. Some of the colorful clouds in the image could be hiding supernova remnants.

2026 July 15

Gigantic Jet Over the Tatacoa Desert Image Credit & Copyright: Mario Vargas Text: Keighley Rockcliffe (NASA GSFC, UMBC CSST, CRESST II)

Explanation: Is there an angry Sith using force lightning in the Tatacoa Desert? This is not science fiction, but a gigantic jet with multiple red streamers! Ordinary lightning occurs when thundercloud particles collide, lose their electrons, and build up negative charge at the cloud bottom. The cloud's negative charge repels negative charge deeper into the Earth, leaving Earth's surface positively charged. The opposite charges attract, reaching towards each other and superheating the air into a white strike of plasma. A gigantic jet occurs when internal cloud discharge escapes upward through a weak positive shielding layer, and shoots up from the cloud in less than a second. They extend up into the mesosphere where the air is too thin for thunder. The streamers at the top may resemble red sprites and get their color from heated molecular nitrogen.

2026 July 14

Double Lobed Asteroid Torifune Image Credit & Copyright: JAXA, U. of Tokyo, Chiba Tech, Tokyo U. of Science, AIST, Paris Obs., IAC

Explanation: Why is this asteroid a double? Earlier this month the Japanese robotic spacecraft Hayabusa2 shot past asteroid 98943 Torifune and captured pictures. Although previous observations from distant Earth indicated that Torifune was oblong, Hayabusa2 found that Torifune actually has two joined lobes. With a length of about four soccer fields, this space rock frequently comes near the Earth as it orbits the Sun, although it is not a threat. Besides the two lobes, Torifune shows many large boulders, but, surprisingly, no obvious craters, likely because its surface is a pile of rubble. Like asteroid Arrokoth, it appears that each lobe formed separately before colliding and becoming stuck together. Hayabusa2 famously encountered asteroid Ryugu in 2018, and now heads for an encounter in 2031 with 1998 KY26, a smaller asteroid that rotates unusually fast and might have reservoirs of ice.

2026 July 13

Auroras from Space Image Credit: ESA, NASA, ISS Expedition 74; Capture: Sophie Adenot; Music: Circle of Light (Patrick Hawes & Grace Davidson)

Explanation: What do auroras look like from above? Behold! From the ground, auroras dance high above clouds, frequently causing spectacular displays. From space, they look a bit different. As the International Space Station (ISS) circles the Earth every 90 minutes, it sometimes sees auroras below that are active on the night side. A one-hour time-lapse video showing auroras from above was captured about two weeks ago from the orbiting ISS. The ISS -- and all objects in low Earth orbit -- will pass well above green auroras but just a bit above red glowing auroras. The auroras' electron and proton streams are too thin to be a danger to the ISS, just as clouds pose little danger to airplanes. From orbit, as magnetic fields change, auroras can appear to squiggle and crawl like giant snakes. The featured one-minute video was captured by French astronaut Sophie Adenot of the ISS Expedition 74 crew.

2026 July 12

Galaxy NGC 474: Shells and Star Streams Image Credit & License: CFHT, Coelum, MegaCam, J.-C. Cuillandre (CFHT) & G. A. Anselmi (Coelum)

Explanation: What's happening to galaxy NGC 474? The multiple layers of emission appear strangely complex given the relatively featureless appearance of the elliptical galaxy in less deep images. The cause of the shells is a topic of research, but they are possibly tidal tails related to debris left over from absorbing numerous small galaxies in the past billion years. Alternatively, the shells may be like ripples in a pond, where the ongoing collision with the spiral galaxy just to the right of NGC 474 is causing density waves to ripple through the galactic giant. Regardless of the actual cause, the featured image dramatically highlights the increasing evidence that the halos of some elliptical galaxies are surprisingly complicated. Similarly, the halo of our own Milky Way Galaxy is one example of such unexpected intricacies. NGC 474 spans about 250,000 light years and lies about 100 million light years distant toward the constellation of the Fish (Pisces).

2026 July 11

Messier 24: Sagittarius Star Cloud Image Credit & Copyright: Chuck Ayoub

Explanation: Unlike most entries in Charles Messier's famous catalog of deep sky objects, M24 is not a bright galaxy, star cluster, or nebula. It's a gap in nearby, obscuring interstellar dust clouds that allows a view of the distant stars in the Sagittarius spiral arm of our Milky Way galaxy. Direct your gaze through this gap with binoculars or a small telescope and you are looking through a window over 300 light-years wide at stars some 10,000 light-years or more from Earth. Sometimes called the Small Sagittarius Star Cloud, M24's luminous stars stretch across this gorgeous interstellar scene. Spanning over four full moons on the sky toward the constellation Sagittarius, the telescopic field of view includes dark markings B92 and B93 near the center of M24, along with other clouds of dust and glowing nebulae toward the center of the Milky Way.

2026 July 10

Western Moon, Eastern Sea Image Credit & Copyright: Guy Bardon

Explanation: The Mare Orientale, Latin for Eastern Sea, is one of the most striking large scale lunar features. The youngest of the large lunar impact basins it's very difficult to see from an earthbound perspective. Still, captured on July 7 during a period of favorable tilt, or libration of the lunar nearside, the Eastern Sea can be found at the upper right in this sharp telescopic view. In the image, the large lunar mare is extremely foreshortened and stretches along the Moon's western edge. Formed by the impact of an asteroid over 3 billion years ago and nearly 1000 kilometers across, the impact basin's concentric circular features are ripples in the lunar crust. But they are a little easier to spot in more direct images of the region taken from lunar orbit. So why is the Eastern Sea at the Moon's western edge? The Mare Orientale lunar feature was named before 1961. That's when the convention labeling east and west on lunar maps was reversed.

2026 July 9

The Red Glow of the Cosmic Bat Nebula Image Credit & Copyright: Humbert Cédric Text: Keighley Rockcliffe (NASA GSFC, UMBC CSST, CRESST II)

Explanation: This Cosmic Bat wishes you a happy Summerween! This mid-year celebration of Halloween transcends hemispheres, even though summer in the Northern hemisphere is winter in the South. Contrary to its eery aura, the Cosmic Bat Nebula (LDN 43), not to be confused with the Bat Nebula (NGC 6995), is a vibrant birthplace for stars. A bit of young starlight peeks through the dense clouds of gas and dust that make up the Cosmic Bat’s 12 lightyear wingspan. The ultraviolet light from the young stars energizes the nebula’s hydrogen gas, causing it to glow an ominous red. The jet of glowing hydrogen gas emerging from the bat’s head hints at the star formation hidden within.

2026 July 8

Swift Boost Mission Image Credit: Katalyst Space Text: Cecilia Chirenti (NASA GSFC, UMCP, CRESST II)

Explanation: Sometimes we can all use a little help from a friend. NASA's Neil Gehrels Swift Observatory needs a boost to stay in orbit after almost 22 years of service. This video shows an artist's visualization of the Swift Boost Mission: The Katalyst's LINK spacecraft was launched aboard a Northrop Grumman Pegasus XL rocket on July 3 and it is now en route to rendezvous with Swift and boost it to a higher orbit over the course of the next several months. This type of maneuver has never been attempted before. If successful, it will be the technology demonstration of a new key capability to extended the lifetime of spacecraft in low Earth orbit, whose orbits decay over time. Swift has an array of instruments that observe the most energetic explosions in the Universe in gamma-rays, X-rays and ultraviolet, and the unique ability to repoint in their direction within tens of seconds. Astronomers around the world, and indeed all fans of cosmic explosions, are anxiously hoping for a successful mission!

2026 July 7

NGC 6188: Dragons of Ara Image Credit & Copyright: Rod Prazeres

Explanation: Where can you find dragons fighting in the night sky? In the southern constellation of the Altar: Ara. The dragons are, of course, actually made of suggestively shaped gas and dust. The celestial home of the mythological battling beasts is cataloged as NGC 6188 and located about 4,000 light years away near the edge of a large molecular cloud. Massive, young stars of the embedded Ara OB1 association were formed there only a few million years ago, sculpting the dark shapes and powering the nebular glow with stellar winds and intense ultraviolet radiation. Joining NGC 6188 on this cosmic canvas, visible toward the lower right, is unusual emission nebula NGC 6164, also created by one of the region's massive stars. This impressively wide field picture, captured from Queensland, Australia, spans over 2 degrees (four full Moons).

2026 July 6

Dueling Bands over the Atacama Desert Image Credit & Copyright: Julien Looten

Explanation: What are these two bands in the sky? The more commonly seen band is on the left and is the central band of our Milky Way galaxy. Our Sun orbits in the disk of this spiral galaxy so that from inside, it appears as a band of comparable brightness all the way around the sky. The less commonly seen band, on the right, is zodiacal light -- sunlight reflected from dust orbiting the Sun in our Solar System. Zodiacal light is brightest near the Sun and so is best seen just before sunrise or just after sunset. On some evenings, this ribbon of zodiacal light can appear quite prominent. It was discovered only in this century that zodiacal dust was mostly expelled by comets that have passed near Jupiter. The featured image was captured about a year ago from the Atacama Desert in Chile.

2026 July 5

Saturn's Iapetus: Painted Moon Image Credit: NASA, ESA, JPL, SSI, Cassini Imaging Team

Explanation: What has happened to Saturn's moon Iapetus? Vast sections of this strange world are dark as coal, while others are as bright as snow. To help better understand this unusually tinted moon, in 2007 NASA directed the robotic Cassini spacecraft then orbiting Saturn to swoop within 2,000 kilometers. Pictured here, from about 75,000 kilometers out, is the hemisphere of Iapetus that is always trailing. A large impact crater seen in the south spans 500 kilometers and appears superposed on an older crater of similar size. The dark material is seen increasingly coating the easternmost part of Iapetus, darkening craters and highlands alike. A leading hypothesis is that the dark material is mostly a form of carbon-rich soil leftover from when relatively warm but dirty ice sublimates. An initial coating of this dark material may have been effectively painted on by the accretion of meteor-liberated debris from other moons.