Wednesday, October 31, 2012

Mars surface pics

Most of the rock surfaces in Gale Crater are covered by dust, making many photos have very low contrast and with little variation in color. By stretching each color to near the full range available, small differences are emphasized. The bluish tones here are not near the true colors, but are blue only in comparison to other surfaces; because the dust is redish, blues and greens are stretched more.

Most of the variation appears to be due to differing thickness of dust on the surfaces.

These Curiosity photos are from the mast cameras.

Original imagetaken: 2012 SEP 29 09:12:44 EDT
river gravel?
Original imagetaken: 2012 SEP 29 09:13:36 EDT

Tuesday, October 23, 2012

Programmers Anonymous notes, 1101

Cellular automata are implemented as rules on a discrete grid. This seems to limits the range of possible behaviors, as the rules depend on a finite number of neighbors. SmoothLife is also implemented on a (rectangular) grid, but the rules approximate continuous functions on a large set of neighbors. Finding parameter sets that display interesting behavior is more difficult, but this example shows that motion of coherent structures (gliders) in any direction is possible. Source code. Paper describing the implementation.

Learnable Programming

A visual interface designer with a huge ego criticizes the way everyone else programs:
The goals of a programming system should be:
  • to support and encourage powerful ways of thinking
  • to enable programmers to see and understand the execution of their programs
A live-coding Processing environment addresses neither of these goals. JavaScript and Processing are poorly-designed languages that support weak ways of thinking, and ignore decades of learning about learning. And live coding, as a standalone feature, is worthless.
Alan Perlis wrote, "To understand a program, you must become both the machine and the program." This view is a mistake, and it is this widespread and virulent mistake that keeps programming a difficult and obscure art. A person is not a machine, and should not be forced to think like one.

Relatively Prime's Chinook podcast

Chinook is the greatest checkers player in the world, in fact it is impossible to beat. The product of an 18 year project in computer artificial intelligence, Chinook represents one of the greatest breakthroughs in computer game playing and was the first machine to ever hold a human world championship. (Relatively Prime, stories from the mathematical domain)

Chinook's story is a bittersweet and moving tale, a modern account of John Henry and the steam-drill, though this version is told from the point of view of the machine and its maker, Jonathan Schaeffer, a University of Alberta scientist who led the Chinook team. Schaeffer's quest begins with an obsessive drive to beat reigning checkers champ Marion Tinsley, but as the tale unfolds, Tinsley becomes more and more sympathetic, so that by the end, I was rooting for the human. (Cory Doctorow's description)

"...a time-ordered stream of documents that functions as a diary of your electronic life; every document you create and every document other people send you is stored in your lifestream. The tail of your stream contains documents from the past (starting with your electronic birth certificate). Moving away from the tail and toward the present, your stream contains more recent documents --- papers in progress or new electronic mail; other documents (pictures, correspondence, bills, movies, voice mail, software) are stored in between. Moving beyond the present and into the future, the stream contains documents you will need: reminders, calendar items, to-do lists."Eric Freeman, David Gelemter in Lifestreams Project Home Page
Lifestreams represent a source of information about people's intents that can be mined.[3] 

Numerical approximations of pi
The English amateur mathematician William Shanks, a man of independent means, spent over 20 years calculating pi to 707 decimal places. This was accomplished in 1873, although only the first 527 were correct. His routine was as follows: He would calculate new digits all morning; and then he would spend all afternoon checking his morning's work. This was the longest expansion of pi until the advent of the electronic digital computer three-quarters of a century later.

Stern–Brocot tree
In number theory, the Stern–Brocot tree is an infinite complete binary tree in which the vertices correspond precisely to the positive rational numbers, whose values are ordered from left to right as in a search tree.
The Stern–Brocot tree was discovered independently by Moritz Stern (1858) and Achille Brocot (1861). Stern was a German number theorist; Brocot was a French clockmaker who used the Stern–Brocot tree to design systems of gears with a gear ratio close to some desired value by finding a ratio of smooth numbers near that value.

Monday, October 22, 2012

Blue capped pillars on Mars

An extraordinary rock formation, photographed with a Curiosity mast camera a few days ago, recieved and released today.

[10/26/12: See update at bottom, from a JPL video that gives a better but incomplete description of what they know about this feature they call "Zephyr" or "Stonehenge".]

It appears to be a row of harder bluish rock blobs with the underlying substrate rock partially eroded away. Is it a ventrifact? Presumably most erosion is due to wind driven abrasion. These pillars are vertical and sandblasting would be expected to undercut harder material, but it's strange that the pillars survived. The bluish caps have a slightly specular surface, and look like they may be translucent with a distinct lower boundary and opaque supporting rock.

The three dark "holes" in the sand behind the pillars are remains after Curiosity laser blasting.

blue capped pillars
There doesn't appear to be any sort of continuation of the form, as you might see in an eroded dyke.

I'm guessing they are agate:
Most agates occur as nodules in volcanic rocks or ancient lavas where they represent cavities originally produced by the disengagement ofvolatiles in the molten mass which were then filled, wholly or partially, by siliceous matter deposited in regular layers upon the walls.
In the formation of an ordinary agate, it is probable that waters containing silica in solution—derived, perhaps, from the decomposition of some of the silicates in the lava itself—percolated through the rock and deposited a siliceous coating on the interior of the vapour-vesicles.  

Original image

JPL is on it. Here's a ChemCam photo. Notice that the three "holes" (and a fourth, less visible) in the sand behind the formation don't appear in this shot (see below for comparison after shot), but the shadows are in a similar position (a slightly higher sun angle). A close-up photo is needed, if only for the beauty and mystery.

Original imagetaken: 2012 OCT 17 20:45:59 EDT

Original imagetaken: 2012 OCT 17 21:03:22 EDT, 17 minutes and 22 seconds after the above image. There are also disturbances below the pillars, near the shadow line.

Drat, it missed!! More target practice required, autonomous mode. Don't these robot overlords practice with shoot-em-ups?

I count six misses, including a couple at the base of the pillars, and some pebbles scattered.

1/23/12 New photo that's more in focus showing that Curiosity had a direct hit, although it is close to the boundary between the blue cap rock and substrate.

Original imagetaken: 2012 OCT 23 00:37:01 EDT

Here's the comparison, coregisteed to the single "before" image.

No word yet from JPL on whether they saw a silica signal to be expected from an agate.

From 10/26/12 JPL podcast and YouTube video:

This feature is really only an inch long and we're shooting this from about 8 feet away, making the pointing very difficult.  So that's why we decided to do 9 points instead of just 2, just to make sure we would hit the material of interest. We ended up hitting both the dark and the light material and we found that there was indeed a compositional difference. 
1" scale bar

This feature is really only an inch long and we're shooting this from about 8 feet away, making the pointing very difficult.
JPL marking of laser hits
You can see that this isn't a good representation of where the laser actually hit: two or three of them are just wrong. It's irritating that JPL hasn't released data or results of the spectroscopy.

Saturday, October 20, 2012

Bit of trash on Mars, stereo pair

Stereo pair of a patch of pebbles, dust and a scrap of distressed pastic (about 13mm long), using Curiosity's Mars Hand Lens Imager (MAHLI). The camera was shifted by about 7mm between the views.

NASA speculates that the plastic was part of the delivery vehicle, presumeably shredded during landing and carried by Curiosity to this location about a half-kilometer from the landing site. But if they know what part it is from, they aren't saying.

(stereo pairs, cross-view)

The trash was unexpectedly spotted at bottom center of this photo of the first scoop of soil. It is more visible in the original full size image.

It was a good opportunity to get a high resolution shot of the pebbles covered, and interspersed with, dust.

The two images were taken about 5 minutes apart, with indirect sunlight.

Thursday, October 4, 2012

Closeups on Mars

Photography by Curiosity in Gale Crater:

One corner of a pyramidal rock named Jake Matijevic.
Original: 0044MR0204022000E1_DXXX
Nice wider view
Composition and other information

Sand ripple on patch of ground named Rocknest. I don't know the exact scale, but it looks to be about 30-60 cm wide. The small blobs of texture seem to be pebbles coated in dust.

After a scoop from near the ripple.

The ripple above extends into the foreground of this navigation camera photo, looking to the rim of Gale Crater.

Robot wheel impression across the ridge. The body of the ripple appears to be very fine grained, more like flour than sand.

Top of wheel print above, but with different sun angle (time of sol). Original.

Closeup of part of this wheel-print. Original. The straight horizontal bands are impressions of the wheel surface (see wheel image below).

And closer. Original.

Closer view at edge of imprint:
"The largest grains ... are about 0.04 to 0.08 inches (1 to 2 millimeters) in size. The bulk of the sand in the ripple is smaller, in the range below 0.002 to 0.008 inches (50 to 200 microns).

Wheels of Curiosity that made the impressions. Each is about 40 cm wide. Notice the fine linear texture of the left wheel in the highlight. This pattern is seen as horizontal bands in the dust (two images above, top).