As part of the current show (Worlds of Stone) at Pacific Science Center we’re updating the images we show from NASA’s MESSENGER and Dawn missions on a weekly basis. I’ll try to show them to you the week after we use the in the planetarium.

Dawn

Vesta

NASA Caption

Released November 7, 2011

PASADENA, Calif. — These Dawn FC (framing camera) images show part of Vesta’s equatorial region, which contains a prominent, deep impact crater (lower center of image) and large troughs (linear depressions). The various colors correspond to the height of the area that they color. For example, the white areas in the bottom corners of the image are the highest areas and the blue areas along the top of the image are the lowest. The prominent impact crater is set into a topographically high area defined by the red and white color-coding. Above this area there are a number of deep troughs represented by green and blue color-coding. A conspicuous trough on the left, which looks like it could be quite deep in the albedo image, is shown by the color-coding in the topography image to be only a little shallower than the area surrounding it.
Image Credit: NASA/ JPL-Caltech/ UCLA/ MPS/ DLR/ IDA

Alice Says:

This is a standard terrain image with rainbow colors corresponding to elevation. Pink and white are high elevations, blue and green are low. There’s a weirdness in this one though – the colors go in this order: blue, green, yellow, orange, pink, brown, white. Orange and brown look almost the same.
My favorite feature here is the line running up to the left from the big crater in the middle. Due to the weirdness with the scale, I can’t tell if this is a ridge or a valley. What do you think? I have an e-mail out to JPL.

MESSENGER

Mercury, or a puddle?

NASA Caption

Released November 8, 2011

Date acquired: October 31, 2011

Of Interest: This eastward-looking image shows a wider view of the beautiful unnamed crater highlighted in yesterday’s featured image (center). The complicated folds and fractures that deform the once smooth floor of the Caloris basin can also be seen.
This image was acquired as a high-resolution targeted observation. Targeted observations are images of a small area on Mercury’s surface at resolutions much higher than the base maps. It is not possible to cover all of Mercury’s surface at this high resolution during MESSENGER’s one-year mission, but several areas of high scientific interest are generally imaged in this mode each week.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Alice Says:

If this image doesn’t take your breath away I can’t help you. Those craters look like raindrops in a puddle to me. This picture is so beautiful. Mercury looks like a PLANET here, not just a desolate collection of black-and-white photos. Of note: the bright areas are not highlights, they are crater rays – new dirt (“regolith”) kicked up by recent impacts.

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MESSENGER

Dawn

~ A l i c e !

We opened a new show in the Willard Smith Planetarium at Pacific Science Center. It’s all about NASA’s current missions in the inner solar system: MESSENGER to Mercury and Dawn to Vesta and Ceres.

As part of that show we’re updating the images we show from MESSENGER and Dawn on a weekly basis. I’ll try to show them to you the week after we use the in the planetarium.

Dawn

Boulders on Vesta Image Credit: NASA/ JPL-Caltech/ UCLA/ MPS/ DLR/ IDA

NASA Caption

Released October 12, 2011

PASADENA, Calif. — This detail of a Dawn FC (framing camera) image shows a fresh scarp rimmed crater with many boulders on the crater floor. These boulders have diameters of 100-200m, which is roughly the size of many asteroids! Also evident in this image are linear mass movement features, which originate from the rim of the crater (bottom of image) and are due to material slumping towards the center of the crater. There are also many smaller, and presumably younger, impact craters on the walls of this crater.

NASA’s Dawn spacecraft obtained this image with its framing camera on September 20th 2011.

Alice Says

Let me unpack what NASA said for you:

• “Fresh scarp rimmed crater “ – This crater is new, and it has a sharp edge, like a cliff (a scarp).
• “Boulders on the crater floor. These boulders have diameters of 100-200m,” – That’s those tiny black dots in the middle there.
• “Linear mass movement features” – Dirt moved. It moved in a straight line. The lines you see that go from the edge of the crater in towards the middle are these “linear features.” And technically I shouldn’t call it dirt. Regolith is better, but dirt gives you the right idea.
• “Due to material slumping towards the center of the crater.” – slumping is like sliding. Imagine yourself sitting against a wall. You sit straight at first and then get tired so you scootch down a little, and maybe lean over on your elbow. Slumping is dirt doing the same thing, it’s just … slumped. It’s different that sliding because when you slide you end up all in a completely different place. Slumping you just compact in place, maybe spreading out a little at the bottom.
• “Presumably younger” – when one crater is on top of another you can assume the crater on top is younger.

The boulders (dots) are my favorite part of this image.

MESSENGER

Mercury in Limb-O Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

NASA Caption

Date acquired: September 19, 2011
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
Of Interest: This image provides us with a beautiful view of a portion of Mercury’s southern hemisphere. The bright rayed crater near the limb is Debussy.. Also visible, near the center of the image, is Matabei, a small crater distinguishable by its unique dark rays.
These limb images provide information about Mercury’s shape.

Alice Says

I love bright craters – they’re bright because they’re new, not because their composition is different. So rocks are made of minerals, and minerals are usually crystals: they have a lattice of atoms very perfectly aligned. If you just leave a crystal out on a planet it gets scratched up, banged around and the surface gets marred or weathered. If you crack that crystal open, it cracks (cleaves) along those perfect lattice boundaries, between atoms, exposing a new surface. This surface is perfectly flat –flat at the molecular level!! – and therefore reflective like a mirror. This is a cleavage plane. When you smack a meteorite into a planet, you kick up a bunch of rocks and minerals, cracking them all open along those cleavage planes. These fall back down to the planet, reflective, pretty, and unmarred – which looks from space like a bright white crater and rays.

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MESSENGER

Dawn

~ A l i c e !

NASA’s MESSENGER just did its third flyby of Mercury on September 29th, 2009. It will enter orbit in March of 2011. Here are a few discoveries, with some personal notes and thoughts.

Bright Spot

Credit: NASA's MESSENGER

Interestingly, this bright spot has been seen and photographed only three times – twice by MESSENGER, and the first time from the ground. That ground image was by Ron Dantowitz, one of my coworkers from the Museum of Science! He used the Mt. Wilson Observatory to collect an incredible image.
The light parts are probably kicked-up material from the basin in the middle. Due to the shape and color, the basin may or may not be volcanic in nature. They’re still studying.

Double-Ring Crater

Credit: NASA’s MESSENGER

Ahh, beautiful. Double-ring craters are an indication of a high-force impact – usually a very massive meteorite. There is a “ripple effect” in the rock – like dropping a pebble in a pond – except you’re dropping a rock on a planet. Sometimes you even get a “splash-back” which forms a peak in the middle of the crater.
The rock of the surface of the planet is made molten by the force of the impact, and resolidifies – freezing the ripples in place. You don’t want to be nearby when this happens.

Crater Ejecta and Secondary Impact Chains

Credit: NASA’s MESSENGER

How do you get a string of craters in a very straight line? No … stop. Consider for a moment. You know what? I’m not going to tell you to the end of the post in order to FORCE you to think about it.

Paw Print!

Credit: NASA’s MESSENGER

I couldn’t not include it – it is just too cute!
Now – how did this happen?
You know, for all of the great ideas you just had, this set of craters is coincidence (like the smiley-face crater on Mars). Pretty cute though, right?

Crater Ejecta and Secondary Impact Chains – Continued

Okay, I hope you came up with some creative answers. Often they are caused by a “splash” kicked up when a meteorite forms a crater (in this case called a primary crater), and some of the material tossed up is big enough that when it comes back down it makes a secondary crater.

Now, instead of just one rock being kicked up and away from the primary impact, several are. They all fly off in the exact same direction (away) and when they come down each one makes a secondary crater – and they all occur in a line.

~ A l i c e !

The Key Stuff:

Woo hoo! New images of Mercury!
The way I’d introduce this and interpret it in the planetarium is just to ask questions about it, and collect visitor hypotheses. That’s all the scientists have right now: questions. They also have some hypotheses about bits of it, but they haven’t had time to think of ideas for everything, and even less to test or analyze those ideas.

Mercury Credit: MESSENGER

What’s up with those longitudinal lines?
Why are those rayed craters so bright?
Some of those craters are on the lines, why?
Is that Mercury’s North pole at the top?
What causes lines like that on other planets?

Here’s some background to help you with your analysis.

Rays:

As we know from the Moon, rays often emanate from craters – especially new craters. When the meteor impacts, it sprays up a bunch of regolith (surface rock/dirt) that falls down in a rayed pattern. Go stomp in a puddle. Watch what happens – that’s what I’m talking about.

Bright Craters:

Brighter craters are almost always newer. The rock is newly broken, showing “shiny” un-weathered, un-covered, un-eroded faces to the sunlight which bounces back at us.

North and South:

According to the MESSENGER press release, that is the North Pole of Mercury up there at the top with a crater on it.

Longitudinal Lines:

The MESSENGER team has floated the idea that these are rays from that Northern crater. They know more than me, but that seems to me like a long way for ejecta (the kicked up regolith) to go. A really long way. How hard would that impact have had to be? Would Mercury’s gravity be enough to pull that ejecta back?

Want More?

Emily promises to have a post up soon.
Phil’s already chatting about it.

My Source.

P.S. Phil’s wrong. It’s not a watermelon. It’s a pumpkin, and I have incontrovertable proof:

Mercury is a Pumpkin