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Too steep for ripples

ESP_043085_1670_1.0x A piece of Mars: This 480×270 m (0.3×0.17 mi) area is a steep slope that plunges down to the upper left. A pile of dark sand, covered by brighter tan dust, clings to the hillside. Usually the martian wind blows sand into ripples, and you can see where it’s tried to do that here. But the steep slope triggers thin dark avalanches of dark sand that compete with the wind in shaping the sandy surface. (HiRISE ESP_043085_1670 NASA/JPL/Univ. of Arizona)

Windy windows

ESP_043086_1715_1.0x A Piece of Mars: This 0.96×0.54 km (0.6×0.33 mi) area shows ripples forming on a layer of dark gray material. In a few spots, the gray layer has been eroded away (probably by wind scour), revealing the lighter, tan-colored terrain below. Geologists call these exposures windows, because you can see through one layer to another that’s underneath. (HiRISE ESP_043086_1715 JPL/NASA/Univ. of Arizona)

Crochet ripples

ESP_042360_1755_1.0x A Piece of Mars: This 480×270 m (1575×886 ft) area shows a seemingly endless field of ripples. They’re big, about 50 m (164 ft) from crest to crest, and probably about 5 m (16 ft) high. Is there a knit or crochet pattern out there that looks like this? You could market it to some Mars aeolian scientists… (HiRISE ESP_042360_1755, NASA/JPL/Univ. of Arizona)

Very long ripples

ESP_043098_1650_1.0x A Piece of Mars: Most of the scene (0.96×0.54 km or 0.6×0.34 mi) is one long slope of a dune. The crest is the line in the top right; the ground below is in the bottom left. If you ever walk along a dune or beach, you’ll see small ripples that can reach up to about a meter in length. But the ripples on this dune extend from the crest to the ground – they’re more than half a kilometer (more than a third of a mile) long! (HiRISE ESP_043098_1650 NASA/JPL/Univ. of Arizona)

Thoughts on GPI

In a major breakthrough for exoplanet discovery and exploration, the Gemini Planet Imager (GPI) is proving to be one of most powerful and effective instruments ever invented for directly imaging planets in orbit around other stars.

An artistic conception of the Jupiter-like exoplanet, 51 Eri b, seen in the near-infrared light that shows the hot layers deep in its atmosphere glowing through clouds. Because of its young age, this young cousin of our own Jupiter is still hot and  carries information on the way it was formed 20 million years ago.  credits: Danielle Futselaar & Franck Marchis, SETI Institute

An artistic conception of the Jupiter-like exoplanet, 51 Eri b, seen in the near-infrared light that shows the hot layers deep in its atmosphere glowing through clouds. Because of its young age, this young cousin of our own Jupiter is still hot and carries information on the way it was formed 20 million years ago.
credits: Danielle Futselaar & Franck Marchis, SETI Institute

The behind-the-scenes story of this project sheds light on the complexities and challenges of designing and building a truly game-changing instrument. We started work more than thirteen years ago under the leadership of Bruce Macintosh and the auspices of the Center for Adaptive Optics. At that time, a number of scientists, most from California and Canada, met to discuss building a groundbreaking adaptive optics (AO) system powerful enough to confront — and overcome — the challenging of directly collecting photons from young Jupiter-like exoplanets. The discovery of 51 Eri b, which was announced last August, is the culmination of that effort. 


A light touch

ESP_042691_2060_0.15x A Piece of Mars: This 3.2×1.8 km (2×1.1 mi) area shows terrain covered by bright dust. Dark stripes are areas where wind has lightly scoured the surface, revealing the dark material beneath. Faint bright lines criss-cross the surface – these are tracks left by dust devils. The dust devils disturb the surface but don’t lift up enough dust to reveal the darker surface underneath. (HiRISE ESP_042691_2060, NASA/JPL/Univ. of Arizona)

Our Predictions about Pluto: Getting it Right/Getting it Wrong

Family portrait of Pluto's four small moons

Family portrait of Pluto’s four small moons

Back in June, my research colleage Doug Hamilton and I put out a paper in Nature magazine about the four small moons of Pluto. The timing was not accidental. Although the paper was the culmination of years of work with the Hubble Telescope, we knew that a lot of our predictions would be tested barely a month later, when the New Horizons spacecraft passed Pluto. Making predictions that might be proven wrong is part of the fun, and also part of the danger, of scientific research.

As we all know, the flyby was a great success and we are now waiting, patiently, for the slow trickle of images and other data to come back from the spacecraft. Today, NASA has released the first “family portrait” of Pluto’s four small moons. As someone who has spent years studying these objects as nothing but faint dots, I find it is enormously gratifying to see them as resolved bodies, with shapes, colors and surface features.

So what did we get right? Well, based on years of studying how the brightness of each body varies, we were able to determine the rough shapes of the two larger moons, Nix and Hydra. On that point, we nailed it! Also, by making assumptions about how bright the surfaces are, we could make estimates of their sizes. We have learned that the moons are a bit brighter than we expected, and therefore a bit smaller, but overall our predictions have held up well.

…with one big exception–Kerberos. Our paper predicted that Kerberos would be big and dark, whereas the image clearly shows an object that is small and bright. What went wrong? Well, it all comes down to the moons’ masses—how much they would weigh if you could put them on a scale. The only way to determine the masses of these moons is to study how each one subtly alters the courses of the others. Based on years of precise measurements, our colleagues believed that they had weighed Kerberos, and its mass was surprisingly high–about a third that of Nix and Hydra. On the other hand, from our measurements, it only reflected about 5% as much sunlight. The only way to make an object that faint and that massive is to make it very very dark. That darkness, comparable to that of a charcoal briquette, is not out of line with other bodies in the outer Solar System, but it certainly made it different from its Plutonian siblings.

We know now that Kerberos is small and bright. If the mass determination is right, then Kerberos is absurdly dense–many times denser than lead. That seems unlikely. We therefore conclude that we probably had a broken scale. Because weighing the moons of Pluto is such a tough job, this is not out of the question. Now that we have new and more precise measurements of the orbits of the moons, I boldly predict that we will soon learn that the mass of Kerberos is much lower than we had previously thought.

One word of caution, however: my bold predictions don’t always turn out to be right.

Peas in a pod

ESP_042697_2055_0.5x A Piece of Mars: These “peas-in-a-pod” are dunes covered in long ripples (the scene is 960×480 m, or 0.6×0.3 mi). They’re a bit odd, surrounded by a rippled apron. It reminds me of melted-looking dunes that are common in high southern latitudes, but these are at 21.5ºN. Yet more Mars mysteries to solve… (HiRISE ESP_042697_2055 NASA/JPL/Univ. of Arizona).

Is it windblown or not?

A Piece of Mars: This scene is 0.96×0.54 km (0.60×0.34 mi) across. There’s an old river valley running across it. The walls of the valley have been eroded and there’s a washboard pattern with a wavelength of ~6m (20 ft). When I first saw this image I thought it was exposed, tilted layers, but a closer look reveals a much smaller (and younger) set of ripples that are similarly oriented and almost certainly formed by the wind. What do you think? (HiRISE ESP_041982_1535, NASA/JPL/Univ. of Arizona)

Parental organizational states

There are three states of parental organization. I’ve done all three on occasion, but I do have my tendencies. We all have our way of getting things done. Here they are:

1. Super organized parent: These are the folks who know where every thing is, and everything has its place (you can tell where the place is, because the things are there, in their place). Appointments are made ahead of time, marked on a calendar, all people who should know about said appointments are informed (possibly more than once), and all required attendants show up at said appointments on time. My mother in law is one of these people. Sometimes she’ll find a stray kid’s sock that we left behind at her house, and she’ll keep it and tell us about it, because to her this is a Problem. She’s actually surprised at stray socks, because in her world they are an oddity. They are worth discussion, and they are even pondered. I’m rarely this organized, but it does happen on occasion, and then everybody is surprised (more discussion and pondering usually ensues).

2. Sporadically-organized parent: This is the parent who remembers to register for summer camp the day before it begins, hoping it’s not too late. The parent who once bought a package of wipes for the car, and who might even know if it’s getting close to empty, but might forget to buy more on their next shopping trip. The parent who usually does the kids’ laundry on time, but every once in a while forgets and the next morning has to go digging through the drawers to find clothes for the kids that aren’t too torn or too small, all while urging sleepy children to wake up and get their teeth brushed. I usually fall into this camp. Hey, this time I registered the kids for gymnastics a whole week ahead of time. Go me!

3. Disorganized parent: You know what this is, I don’t have to tell you. We all have our fuzzy moments. (OK, maybe my mother in law doesn’t. She has skillz.) I sometimes slip in this direction. But here’s thing thing about being in a disorganized parental state, which is why I don’t worry about it too much: sometimes it works for me. Take what happened to me tonight (which prompted me to write this whole thing). My oldest is 5, and he’s got some sort of stomach bug. On the way home from my in-laws’ this evening, he announced that he had to throw up. I’m surprised by this, because he hasn’t thrown up all day, so I haven’t thought about this ahead of time (I’m not the super-organized type, remember). But. On the floor of my (messy) car, among other oddities, is a plastic bag with a bunch of party favors that I got for my kid’s birthday party. Not the birthday party we threw a week ago, but the one last year, because I guess I forgot about those party favors and they didn’t make it into the party favor bags for the guests. So yes, there’s been a plastic bag with about 20 little plastic rings with big googly eyes on them sitting on the front passenger floor of my car for about a year. So I pull over, dump the googly-eyed rings on the car floor, and get the bag to him, in time to get most of the throwup in it. I’m very grateful the bag didn’t have holes.

See, if I’d been super organized, I’d have had a box of Ziploc bags or something at all times, plus some wipes. That would have been nice, but that’s also a lot of spare cycles my tired brain doesn’t want to have to worry about, along with all the other spare cycles that being super organized requires.

If I’d been sporadically-organized, I’d have eventually found that bag of googly-eyed rings sometime over the last year (perhaps while cleaning my car – don’t laugh, I actually cleaned out my car once) and put it somewhere sensible (wherever one stores such things, to be found in time for the next year’s birthday party – because they didn’t make it in this year either), and thrown away the bag. So then I would have had nothing to hand my kid. I’d have been screwed. (On the other hand, I might have had some wipes on hand, which would have been nice.)

But no, in this case I was simply disorganized. So I had the bag, and the evening was not a complete parental failure. Disorganized parenting FTW!