She Started Sleeping

Hey, what happened with Spirit, one of Mars Exploration Rovers?
The rover team can not get the response from Mars.

http://www.jpl.nasa.gov/news/news.cfm?release=2010-252&cid=release_2010-252&msource=2010252&tr=y&auid=6731633

It is winter in the area where she is working. Apparently, she can not move because of cold.
Although they are designed to work for one or two years, they have been working for 6 years!!!
In several years, they have worked hardly.
In this picture, Spirit has a mobility trouble. Her left-front wheel is caught by sand.
Maybe, she became tired after her hard work.

Desert on Titan

Wow! I found this picture on NASA's web site!

http://www.jpl.nasa.gov/news/news.cfm?release=2010-251&cid=release_2010-251&msource=c20100729&tr=y&auid=6723160


The upside picture is the surface of Titan, the largest moon of Saturn, and the downside picture is Namibian desert.
Their sand dunes look similar. Scientists says that the atmosphere of Titan causes this pattern.

I want to look at the colored surface of Titan.

Catenary

It has been long time since I posted last one.

I was thinking about catenary (Not only this one).
When I was a child, I thought the shape of a hanging rope was the parabola.
But, it is actually the other like called catenary.

Catenary is expressed like this.
y=a cosh(x/a)

The method how to derive the expression is explained here. (this page is Japanese)
http://aozoragakuen.sakura.ne.jp/taiwa/taiwaNch04/node48.html