The Lunar Reconnaissance Orbiter has been circling the Moon since 2009, taking thousands of images in amazing resolution unseen since Apollo. Many of these pictures have been simply astonishing, including the one above taken in March 2011: an unnamed crater a few kilometers across (the image is 2.2 km or about 1.4 miles wide). Whatever smacked into the Moon all those eons ago blew out a lot of dust and other material that fell back to the surface, spreading out like the broad petals of a flower. In the crater floor you can barely see some boulders and other debris that must have gone straight up and back down after the impact. The Moon has no air, but formations like this erode after time anyway: countless meteorite impacts, the solar wind, and even thermal flexing during the Moon's day/night cycle take their toll. So we know that such craters must be young, but that's a relative term: this impact may have occurred when dinosaurs still walked the Earth.
Image credit: NASA/GSFC/Arizona State University
In late 2010, an amateur astronomer noticed an odd white spot in Saturn's northern hemisphere. It was a storm, like a gigantic hurricane, which quickly grew in size to thousands of kilometers across and rapidly surpassed the diameter of our own planet. And yet it continued to grow, and in February 2011 the Cassini spacecraft orbiting Saturn took this incredible picture showing the storm had grown so long it had literally wrapped its way around the entire planet! At this point, it was a staggering 300,000 km (180,000 miles) in length -
the same distance as 3/4 of the way from the Earth to the Moon!
Pictures taken in late 2010 and early January also show details of the storm in psychedelic false color, where the whorls and vortices of the raging weather are clear. Saturn's face is usually far more subtle and calm than this - look at the nice, smooth southern hemisphere for comparison - so the eruption of this storm was a surprise to astronomers... but surprises are good, because in many cases that's how we learn things. And I'm glad Cassini was there to get these amazing close-up shots.
Image credit: NASA/JPL-Caltech/SSI
In March of 2011, the spacecraft MESSENGER became the first ever moon of Mercury, taking unprecedented high-resolution images of the solar system's smallest official planet. But while it was on its tortuous path to Mercury, engineers back home programmed the spacecraft to take a series of snapshots, pointing the cameras painstakingly across the solar system. The result is what you see above: every planet in the solar system, a sort of cosmic family portrait.
Uranus and Neptune are there, but too faint to see (you should grab the bigger version of this to see the details). Venus was relatively close to MESSENGER at the time, and so is very bright. My favorite part of this, though, is being able to see the Earth and Moon together. There's something eerie about seeing them both in pictures at the same time, nearly lost in the black (the Jupiter-bound spacecraft Juno took a similar shot of our world this year as well).
It really brings home - well, so to speak - the fact that we are a speck of dust floating in space, tiny to the point of insignificance when seen like this. And yet, never forget that we are significant: after all, we created the machine that took this picture! I think it says a lot about us humans that not only do we send spacecraft to other worlds, but we take the time to make pictures like this. Sometimes, just sometimes, people are pretty cool.
Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of WashingtonOriginal image
The twisted magnetic fields inside of sunspots have as much or more effect on the Sun's outer layers as the gravity of our star itself. As the field lines tangle up, vast towers of ionized gas (called plasma) can erupt, sometimes collapsing back onto the solar surface, and sometimes blasting off into space. These are called prominences, and can take on all sorts of fantastic shapes, usually in the form of plumes or arcs.
Solar photographer Alan Friedman took these two shots of two different prominences, both of which made me laugh when I saw them: the top one looks like a cat nuzzling the Sun, and the bottom one like a dragon!
Expect to see more pictures like this over the coming years, as the Sun's activity gets even more common. Hopefully, we'll also see a dog, and perhaps St. George.
Image credit: Alan Friedman
Saturn and its rings are a continuously-playing show of beauty and grace, but the giant planet also has a vast retinue of moons, each as different from each other as any family of siblings (which make it very hard to pick my favorite from ones like this or this). The biggest, the aptly-named Titan, is a monster, bigger than the planet Mercury and possessing an atmosphere of nitrogen that's twice as thick as Earth's! The atmosphere is so thick and opaque that it blocks our view of the ground in visible light. Infrared light can penetrate that gloom, though, and it's not by coincidence that the Cassini spacecraft is equipped with filters and detectors designed to look in those wavelengths.
Using that equipment, astronomers created the first-ever multicolor map of the surface of Titan (a map using a single color was created in 2009). This false-color map shows elevated regions (white areas), lakes of liquid methane and ethane near the north pole of the moon, and what's most amazing to me, vast areas of wind-blown dunes (shown in brown)! Those aren't grains of sand in the dunes, but grains of frozen hydrocarbons, blown across the plains by Titan's thick air. Detailed radar observations by Cassini show them to be much like dunes on Earth, but a bit chillier: the temperature on the surface of Titan is a numbing (or perhaps I should say "shattering") -180°C (-300°F).
And yet, it's a world not so different than ours: atmosphere, liquid lakes, wind... and at those temperatures, the chemistry of methane is similar to that of water at room temperature on Earth. It's not crazy to wonder if there's life on Titan...
Image credit: NASA/JPL/University of Arizona/CNRS/LPGNant
Of all these pictures of our planetary neighbors, I think I might love this one the most. That's us: it's home. Blue, with feathered white, the only planet to really look this way (Uranus and Neptune are both blue, but for different reasons; we have water, they have methane). This picture is from Terra, a NASA Earth-observing satellite, designed to look down and investigate our environment.
But that's not why this picture really amazes me. Look at it more carefully: almost all you see is water! If you look to the upper right you'll see the west coast of the US, Baja California, and Mexico. Everything else you see is ocean. The satellite was over the Pacific when this was taken, and that expanse of water is vast, covering nearly an entire hemisphere of the planet. It's a coincidence that this is the way things are right now; continental drift changes the sizes of the oceans over geologic time scales. But still, it's a sharp reminder of just how much water we have here on Earth, and why we look for it so steadfastly on other worlds, and why we need to take our job as planetary caretakers more seriously.
Image credit: NASA
Solar eclipses are relatively rare events on the Earth's surface. The Moon's orbit around the Earth is tilted a bit with respect to the Earth's orbit around the Sun, so the Moon has to be at the right place at the right time to block the Sun.
But what if you're in orbit around the Earth? In that case, the Earth itself blocks the Sun all the time (of course, if you want to be pedantic, it happens to us on the surface every time the Sun sets). NASA's Solar Dynamics Observatory stares at the Sun 24/7/365, and was placed in an orbit to minimize the amount of time the Earth blocks its view. But it does happen twice a year, when the orbits all align.
The picture above is from late March 2011, during one of these eclipse seasons. The edge of the Earth cut right across the disk of the Sun, creating this odd view. This particular shot is in the ultraviolet, where Earth's atmosphere is almost opaque, completely cutting off the Sun's light... except for that one little curlicue on the left. That's an extremely bright filament of material, luminous enough to have some of its light get through, despite our atmosphere.
This is a weird and wonderful picture, accessible only from space, which is why I picked it for this year's list.
Image credit: NASA/GSFC/SDO
When I was a kid (mumble mumble) years ago, asteroids were just points of light in even the biggest telescopes. That was true even just a few years ago, but in recent times we've seen quite a few close up thanks to the space program. Vesta is the second largest asteroid, orbiting the Sun in the main belt between Mars and Jupiter. And despite its size (roughly 500 km or 300 miles across), until a few months ago we really didn't know much about it.
But then in July 2011, the spacecraft Dawn arrived. Orbiting the rock, it's been snapping away, revolutionizing our understanding of asteroids. Vesta's landscape is diverse, with craters, cliffs, mountains, and long, linear grooves (although, interestingly, no hints of vulcanism, when some were expected). Its south pole is an enormous impact basin; something huge hit Vesta hard a long time ago. Ejected material from that impact scattered across the solar system, and some of it has hit Earth as meteorites. We've found some of these, and through chemical analysis shown they are from Vesta, which is truly amazing when you think about it. It took a lot of effort to get a spacecraft to the asteroid, and all that time we had pieces of it here already!
But that's OK. There's still plenty left to learn. And eventually Dawn will leave Vesta and head over to Ceres, the largest asteroid in the solar system. What will it find when it gets there?
Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
I really like pictures of Earth from space, but this is one only a mother could love. It's not actually a picture, but a map of Earth's gravity! It's a model created using data from the European Space Agency's orbiting GOCE satellite, which was used to very carefully map out the changing strength of Earth's gravity over our planet's surface. Essentially, this map tells you the direction of "down" over every point on the Earth. If you stand near a mountain, for example, then the gravity of that mountain pulls on you a little bit, and the direction you feel gravity pulling you changes a wee bit.
This kind of map - called a geoid - is a standard reference used by topographic maps, and also helps scientists understand how ocean currents flow, how ocean water circulates, and even better understand the dynamics of sea wave heights. It may make the Earth look lumpy and distorted and weird, but hey - nature calls 'em like it sees 'em.
[Bonus: Nathanial Burton-Bradford took several of these images and created red/green 3D images of them!]
Image credit: ESA/HPF/DLR
This may look like a picture of the Moon taken through a small backyard telescope, but it's anything but: it's a huge mosaic of 1300 images from the Lunar Reconnaissance Orbiter, painstakingly stitched together to make a huge high-res map of the Moon. The bigger version gives you a taste of what's in it (a labeled one is available as well) but even that pales in comparison to the massive 24,000 x 24,000 pixel full size version, weighing in at an astonishing 550 megabytes, in case you needed to wallpaper your living room. If you prefer to interact a bit, then there's a pan-and-scan version where you can zoom in and have fun flying over the lunar surface.
It's more than just fun: one big reason LRO is doing this is to make high-res maps of the Moon for future exploration. It is one of my most fervent hopes that one day, maps like this will be used by people who are trying to find their way from their dome to their in-laws' for dinner.
And if you live on the Moon's far side, no worries: there's a map for that half, too!
Image credit: NASA/GSFC/Arizona State University
We might like to think of the Sun as a steady, calm source of light and heat, but in reality it undergoes a cycle of violent activity driven by magnetic fields. This cycle peaks every 11 years or so, and we're due for the next maximum in 2013 or 2014. The previous minimum lasted an unusually long time, but things started ramping up again in 2011. Sunspots marring the Sun's face started appearing in greater numbers, and many of them were the source of incredible outbursts of energy called solar flares.
This picture shows a flare from August 2011, as seen in the ultraviolet by NASA's Solar Dynamics Observatory. When the subatomic particles spurted out by such flares interact with our own magnetic field, the result can be spectacular aurorae, which are also becoming a common sight. They can also cause blackouts (as a particularly large event did to Quebec in March 1989) and damage our satellites - including GPS and communication satellites. Studying the Sun is more than just science: our economy can literally depend on it.
Image credit: NASA/SDO/AIA
Mars appears to be dead now, but a long time ago it was an active planet. Volcanoes roared, sending floods of lava across the plains of the planet. Sometimes those flows would solidify on top, forming a hollow tube through which the lava moved. Eventually, when the volcano died away, what was left was a hollow underground corridor, called a lava tube.
Sometimes, points along that tube will collapse, forming a hole in the ground above. Called skylights, we see these on Earth near volcanoes, but they're on Mars too! What you're seeing here is just such a skylight. Under this otherwise fairly featureless plain is a lava tube, and something - perhaps a meteorite - punched a hole in it. Sand flowed down, forming the collapse pit, which is about 175 meters (600 feet) across. The hole itself is 35 meters (115 feet) across, the size of a decent back yard. You can even see the rim of the hole casting a shadow on the lava tube floor, 20 meters (60 feet) down!
Skylights on Mars are pretty cool, but they may eventually be useful. The lava tubes are big enough to support a decent size exploration base, and the ground above would protect astronauts from solar radiation. What you're looking at here might very well one day be called "home" by your descendents!
Image credit: NASA/JPL/University of Arizona
Since Pluto's demotion from the brotherhood of planets a few years back, Neptune has taken on the mantle of responsibility of most distant planet in the solar system. It's big, about 4 times the diameter of Earth, but so far away - 4.4 billion kilometers (2.7 billion miles) away at its closest - that even in big telescopes it's hard to see detail. Astronomer Mike Brown used one of the biggest telescopes on Earth, the monster 10-meter Keck eye in Hawaii, to observe Neptune in September 2011, getting this lovely infrared picture of it. The bright bands around Neptune are high-altitude clouds, similar to the cloud patterns we see on Jupiter and Saturn.
And oh, did I say he was observing Neptune? Actually, Mike studies the giant frozen iceballs that orbit the Sun out past Neptune, so really he was more interested in Neptune's moon Triton, seen to the lower right in that picture. Triton is so similar to those other objects that it may actually have once been one, captured eons ago by Neptune's gravity. It's unclear how something like that could've happened, so observations of these distant denizens of the outer solar system are important for us to understand the history and evolution of our local neighborhood.
Image credit: Mike Brown
The MESSENGER spacecraft was launched in 2004 and spent seven years getting to Mercury; it's not all that easy dropping a probe down into the inner solar system. It swung by Mercury twice (not to mention the Earth once and Venus twice!) before finally settling into orbit in March 2011, and then beginning its scientific mission of analyzing the overheated world. Among the first pictures it took was this one, showing the crater named Debussy (after the composer). The crater is 80 km (50 miles) wide, but reaching much farther are those streaks called rays; collapsed plumes of ejected material when whatever hit Mercury hit Mercury. Many craters on the Moon show rays, and in some cases pictures of the two objects look very similar.
Since March, MESSENGER has taken huge amounts of data of the planet, increasing our knowledge of what makes it tick - and it's returned not just images but also laser altimetry data, spectroscopy, and mineralogical maps. Mercury isn't much like Earth at all, but sometimes it's the contrasts that aid our understanding. The planets in the solar system are a diverse lot, and it's only by studying all of them that we can come to understand the one we live on.
Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
A few days ago I posted my favorite space pictures from 2011, and said it was only Part 1. As promised, here is Part 2: my favorite pictures of solar system objects from the past year.
Again, it was ridiculously hard to pick just a few. I had something like 70 to choose from. Our space probes keep sending back amazing shots of planets, moons, asteroids, and more, and we keep getting better at taking pictures of them from the ground as well. As an astronomer, I love it, but as a blogger it makes my fingers cramp.
Still, it's not a terrible burden to bear. All of the pictures I chose are interesting for their beauty, their science, and their story.
To browse, just click the arrows or the next image in the filmstrip. Clicking the image will take you to my original blog post about it, with more information.
... and there's still one more gallery to go! I've done space and now solar system, and that only leaves the rest of the Universe. So stay tuned, there's a whole cosmos coming your way in a few days.