This is a pretty neat picture taken by the Lunar Reconnaissance Orbiter: two craters, side by side:
[Click to impactenate.]
What’s cool about it is the obvious age discrepancy between the two craters. The Moon lacks water and air, but it has erosion nonetheless: micrometeorite impacts, solar wind, and even thermal stress cause by the month-long day night cycle slowly wears away at the surface. Old craters have a rounded look to them, while fresher craters are sharp-edged, and show the debris from impact.
The full-res image has a scale of just a meter per pixel, so a lot of the smaller boulders you see around the younger crater on the right are the size of cars. Both craters are roughly 300 or so meters across; you could walk briskly across them in a couple of minutes.
I noticed the young crater has an odd shape, non-circular, almost diamond-shaped. Then I looked at other, nearby craters, and saw the same thing, so it must mostly be due to lighting. However, there is a funny hillock just to the right of the crater, and the boulder field around it is not symmetric; there are more above and below it. I wonder if there is a density change in the underlying rock just to the right of the crater, which helped shape the crater…?
That area is mostly flat lava flood plains, and in the zoomable and pannable larger-area context image there are some interesting features that look like very old crater rims poking up through the plain. Check it out! One of my favorite things about LRO is the pile of high-res pictures like this one you can zoom in an out of. It really helps give you a feel for what you’re seeing.
Remember last month when I posted that incredible super-hi-res image of the Moon’s near side? A lot of folks asked if an image of the far side were coming soon.
Ask, and ye shall receive.
Holy Selene! Click to enlunanate.
This amazing mosaic is from the Lunar Reconnaissance Orbiter, circling the Moon from a height of a mere 50 km (30 miles) and mapping that entire world. This image is comprised of a whopping 15,000 images from the Wide Angle Camera — yegads! — and shows the side of the Moon we can never see from home.
It looks really different than the near side, doesn’t it? It’s almost entirely craters, while the side we see is dominated by huge lava filled basins called maria (Latin for "seas"). Why is that? Well, it’s known that the crust on the near side is thinner, so it’s easier for big impacts to have punched holes in the crust and allowed magma to bubble up (this was billions of years ago when the inner Moon was still molten).
But why does one side have a thick crust and the other thin? No one knows. Read More
Seen the full Moon lately? Maybe you have, but I can pretty much guarantee you’ve never seen it like this:
[Click to enlunanate.]
Sure, that may just look like another full Moon picture, but it’s much more extraordinary than that: it’s one of the highest resolution pictures of the entire near side of the Moon ever compiled!
This is actually a mosaic of about 1300 separate images taken by the Lunar Reconnaissance Orbiter’s Wide-Angle Camera — the total size is a whopping 24,000 x 24,000 pixels, producing a resolution of about 145 meters/pixel. The full-size version is a monster 550 Mb TIF file (seriously, don’t grab that one unless you need it!), and you can get a more palatable 1400 x 1400 pixel version with labels, too.
The images were taken over the course of two weeks in December 2010. LRO is in a polar orbit around the Moon — think of it as moving in a north/south direction over the surface instead of east/west. Over time, as the Moon rotates underneath it, LRO can see the entire surface of the Moon. As it does this, the angle of sunlight changes, so care had to be taken when creating this mosaic to make it appear seamless; otherwise shadows would appear to jump suddenly from point to point. If you look carefully you’ll see where shadows point in different directions, but it still looks pretty natural.
But it’s not: when you see the full Moon from Earth, that means the Sun is shining straight down on the Moon — the Earth is essentially directly between the Moon and Sun. That means you don’t see any shadows on the surface when the Moon is full. Pictures of it taken from Earth look flat in that case, because our eyes and brains look to shadows to sense the topographical relief — the ups and downs in the surface. But this image shows those shadows, making it a unique view of the full Moon.
The Lunar Reconnaissance Orbiter has a great blog where they post images from the hi-res camera onboard. I was perusing a recent image, and was a bit befuddled:
What the heck? Is this a plateau of some kind? Is that a small dome just below the center of it? The whole thing looks pitted around the edge, too, like some sort of erosion has taken place. But that can’t be right!
Happily, being an old hand with optical illusions, I knew exactly what to do. I flipped the image over, and all became clear: