Tharsis Tholus from Mars Express

Colored elevation image of Tharsis Tholus from directly overhead. Dark blue represents lower elevations, and white the higher elevations. The flanks of the volcano have collapsed in giant landslides at least twice, but interestingly there are no obvious debris piles at the foot of the volcano.

From the European Space Agency: Battered Tharsis Tholus volcano on Mars

The latest image released from Mars Express reveals a large extinct volcano that has been battered and deformed over the aeons.

By Earthly standards, Tharsis Tholus is a giant, towering 8 km above the surrounding terrain, with a base stretching over 155 x 125 km. Yet on Mars, it is just an average-sized volcano. What marks it out as unusual is its battered condition.

Shown here in images taken by the HRSC high-resolution stereo camera on ESA’s Mars Express spacecraft, the volcanic edifice has been marked by dramatic events.

At least two large sections have collapsed around its eastern and western flanks during its four-billion-year history and these catastrophes are now visible as scarps up to several kilometres high.

The main feature of Tharsis Tholus is, however, the caldera in its centre.

It has an almost circular outline, about 32 x 34 km, and is ringed by faults that have allowed the caldera floor to subside by as much as 2.7 km.

It is thought that the volcano emptied its magma chamber during eruptions and, as the lava ran out onto the surface, the chamber roof was no longer able to support its own weight.

So, the volcano collapsed, forming the large caldera.

The summit of Tharsis Tholus, showing its large caldera.

HT: Yahoo News

Snow day and snow maps

The mega-storm that has affected over 100,000,000 people in the United States turned out to be somewhat wimpy here in St. Louis. At our house we got lots of rain, then about 0.25 inches of ice, followed by two inches of sleet, topped by a few inches of snow (hard to tell exactly how much with the wind blowing it around).

I love winter, so I was a bit disappointed. But the kids don’t have school and my wife and I don’t have to go in to work, so we will be out playing in the snow sometime today.

Here are a few maps and images from around the internet, starting with a satellite image showing the size of this storm:

Credit: NOAA

The National Weather Service has a number of static and interactive maps about snow:

Interactive Snow Information map from the National Operational Hydrologic Remote Sensing Center -- http://www.nohrsc.noaa.gov/interactive/html/map.html
Scaled 24-hour Snow Precipitation (rainwater equivalent of snow) -- http://www.nohrsc.noaa.gov/nsa/
Non-Snow Precipitation (There was a lot more to this storm than snow) -- http://www.nohrsc.noaa.gov/nsa/
Snow Depth -- http://www.nohrsc.noaa.gov/nsa/
Current Snow Cover -- http://www.nohrsc.noaa.gov/nh_snowcover/
Current Northern Hemisphere snow cover -- http://www.nohrsc.noaa.gov/nh_snowcover/

Stay warm. Keep Safe. Have fun.

Grace and Peace

New England under water

From the ESRI Map Book Online volume 25: What if all the polar ice melted?

Credit: Paul Jordan, University of Rhode Island

The description from the ESRI Map Book:

This map is a depiction of Rhode Island and southeastern Massachusetts/Cape Cod inundated by a 67-meter (73-yard) sea level rise resulting from a total melting of the polar ice caps. Although an unlikely scenario, the map was created as an attention grabber for display at the University of Rhode Island 2008 Honors Colloquium Lecture Series on Global Warming.

A good map can be artistic as well as informative; in fact the two often go together. The annual ESRI map books are available online or in book form (I am happy to own a couple editions).

Grace and Peace

Arthur C. Clarke and GPS

Science fiction author Arthur C. Clarke was not only one of the first persons to conceive of geostationary communications satellites, he may have also been the first to come up with the idea of the Global Positioning System (GPS). From the Winter 2010/2011 issue of ArcNews: Rendezvous with Reality — Arthur C. Clarke Sees the Future.

Author and futurist Arthur C. Clarke was known worldwide for his science fiction writings, such as 2001: A Space Odyssey and Rendezvous with Rama, but he was also one of the most important visionaries of the last century-most notably, he originated the concept of the geostationary communications satellite in 1945. In 1956, however, Clarke wrote a letter to Andrew G. Haley, president of the American Rocket Society, where he described one potential use for a geostationary communications satellite, to create a “position-finding grid whereby anyone on earth could locate himself by means of a couple of dials on an instrument about the size of a watch”-what we now know as GPS.

The print edition of ArcNews contains a copy of the origin letter along with a transcription. Here’s part of what Clarke wrote:

My general conclusions are that perhaps in 30 years the orbital relay system may take over all the functions of existing surface networks and provide others quite impossible today. For example, the three stations in the 24-hour orbit could provide not only an interference and censorship-free global TV service for the same power as a single modern transmitter, but could also make possible a position-finding grid whereby anyone on earth could locate himself by means of a couple of dials on an instrument about the size of a watch. (A development of Decca and transistorisation.) It might even make possible world-wide person-to-person radio with automatic dialling. Thus no-one on the planet need ever get lost or become out of touch with the community, unless he wanted to be. I’m still thinking about the social consequences of this!

I like that: “No-one on the planet need ever get lost… unless he wanted to be.”

For some reason, the PDF version of ArcNews has a couple of advertisements on page 27 in place of the article on Clarke.

Grace and Peace

P.S. Note that the link to Global Positioning System above takes you to a U.S. Government site written in Chinese. A sign of the times.

New York City — A Montana Native’s Perception

Being that the dreaded Yankees won the World Series, here is my map of New York City, as originally posted in December 2007.

A couple days ago I commented (click here) on a map of Montana printed by The New Yorker Magazine. (I got the map from Strange Maps). Those Easterners know that Montana has everything from militia groups to radical environmentalists, but they didn’t know what part of the state to put them in.

I was thinking to myself: “Hey, you worked as a cartographer for eleven years. You can certainly make just as good of a map of New York City as they made of Montana.” So, here it is:

ny.jpg

I was at JFK airport in 1980, so it isn’t like I haven’t been there.