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Here is NASA's summary of the activities today.

On Sol 52 (Sept. 28), Curiosity drove about 122 feet (37.3 meters) eastward toward the Glenelg area, using visual odometry to assess and adjust for any wheel slippage. The mission's total distance driven has now reached 0.28 mile (0.45 kilometer). The drive brought the rover to a few meters away from an outcrop being considered for an approach drive and subsequent examination with instruments at the end of Curiosity's arm: the Alpha Particle X-Ray Spectrometer and the Mars Hand Lens Imager.

Another priority in coming sols is to reach a location for first use of the rover's capability to scoop up soil material and deliver a sample of it into laboratory instruments.

Activities on Sol 52 included the usual monitoring of the environment around Curiosity with the Radiation Assessment Detector, the Dynamic Albedo of Neutrons instrument, and the Rover Environmental Monitoring Station. A raw image from Curiosity's left Navigation Camera, showing the ground near the rover after the Sol 52 drive, is at

Come out into the tall grass if you want to discuss what our scientist hero friends at NASA mean when they say things like "visual odometry" and "Dynamic Albedo of Neutrons".

These are both very cool things.

First, "visual odometry". The MSL payload sits on surface of a planet that lacks geosynchronous positioning satellites. We have the Mars Reconnaissance mission that can sometimes visualize the rover's position. But for day to day certainty, NASA scientists and engineers built special patterns in the wheels of the rover so that the mast cameras could send images that are used to precisely calculate the platform's movement. As NASA puts it:

NASA's Curiosity rover took its first test stroll Wednesday Aug. 22, 2012, and beamed back pictures of its accomplishment in the form of track marks in the Martian soil. Careful inspection of the tracks reveals a unique, repeating pattern, which the rover can use as a visual reference to drive more accurately in barren terrain. The pattern is Morse code for JPL, the abbreviation for NASA's Jet Propulsion Laboratory in Pasadena, Calif., where the rover was designed and built, and the mission is managed.

"The purpose of the pattern is to create features in the terrain that can be used to visually measure the precise distance between drives," said Matt Heverly, the lead rover driver for Curiosity at JPL.

This driving tool, called visual odometry, allows the rover to use images of landscape features to determine if it has traveled as far as predicted, or if its wheels have slipped. For example, when the rover drives on high slopes or across loose soil, it will routinely stop to check its progress. By measuring its distance relative to dozens of prominent features like pebbles or shadows on rocks -- or patterns in its tracks -- the rover can check how much its wheels may have slipped. If Curiosity has not slipped too much, it can then re-plan the next leg of its drive, taking its actual position into account.

The Dynamic Albedo of Neutrons instrument, DAN for short, looks downward along the rover's path and measures for returns that indicate the presence of water in the upper rock and soil. What that is all about is something called "thermal inertia", which as you have already guessed, means resistance to changing temperature, relative to some other material or place.
Thermal inertia is a physical property of a material. If you know what "inertia" means, "thermal inertia" is exactly what it sounds like: a measure of the material's resistance to changes in temperature. Generally speaking, rocks and water have high thermal inertia. Dust and soil, with their large surface area relative to volume, have low thermal inertia.
As the rover approaches its first major scientific objective at Glenelg, it will also be approaching areas of Gale Crater that satellite mapping indicated have high thermal inertia, which could mean that abundant water still exists on Mars just below the rocky surface.

Here are my previous diaries in this series inspired by NASA's new roving science lab on Mars, listed in the order I have posted them.

Mars Curiosity Rover -- Meet the ChemCam

Ray Bradbury is Honored Today on Mars

What Curiosity Can Do, Part 2.

What Curiosity Can Do on Mars and in this Election

Will Curiosity Mission Finally Vindicate the Life Science Results from the 1976 Viking Lander?

From Mars: SAM Takes a Deep Breath and Flexes his Arm

From Mars: Here's Looking At You, Kid.

On Mars: Super Rover has X-ray Vision

On Mars: Let the Science Begin

On Mars: We have found an Interesting Rock

On Mars: Obama and Biden Campaign This Week

On Mars: Curiosity Does Contact Science

On Mars: A River Ran Through It

Originally posted to Astro Kos on Fri Sep 28, 2012 at 06:58 PM PDT.

Also republished by SciTech and Kossacks on Mars.

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