December 2006 Archives

A Pale Blue Dot

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Earth seen by VoyagerThis 20th of December marked 10 years since the death of Carl Sagan. My first memory of him is of, as a kid, waking up early on Saturday mornings to watch his series "Cosmos". That series has certainly some of the blame for my interest in science in general, as (I'm sure) it does for many people around my age.

Sagan made science popular and cool, and that is his legacy to many, many of us. We all remember him fondly as part of our childhood or youth, and miss him greatly. I will take the opportunity to post some of his (to me) more interesting words.

The picture you see on the left was taken by Voyager 1 in 1990, looking back at the Solar System when it was almost 7 million km away from home. The dot in the centre is Earth, framed by a scattered ray of sun light (the Sun is just outside the field of view). Sagan talked about this image in his book "Pale Blue Dot":

That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar", every "supreme leader", every saint and sinner in the history of our species lived there--on a mote of dust suspended in a sunbeam.

[...]Ann Druyan suggests an experiment: Look back again at the pale blue dot. Take a good long look at it. Stare at the dot for any length of time and then try to convince yourself that God created the whole Universe for one of the 10 million or so species of life that inhabit that speck of dust. Now take it a step further: Imagine that everything was made just for a single shade of that species, or gender, or ethnic or religious subdivision. If this doesn't strike you as unlikely, pick another dot. Imagine it to be inhabited by a different form of intelligent life. They, too, cherish the notion of a God who has created everything for their benefit. How seriously do you take their claim?

Unintentional satellite

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Discovery has already separated from the ISS (and I didn't write much about this mission...) and it's heading home; before that, though, one of the astronauts managed to deploy an unintentional satellite into orbit: her camera. It broke free from its bracket and quietly floated away... The event is, of course, available from YouTube:

(for those reading the RSS feed, the video is here)

What's up in 2007

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A great resource for any amateur astronomer (or, in fact, anyone interested in looking at the sky): Universe Today has a freely downloadable book listing interesting sky phenomena for each day of the year.

The book is richly illustrated (which accounts for the large file size, just over 23MB) and filled with historical information and observing information. You can download the book from Universe Today, or you can get a printed copy from

Liquid water on Mars

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Signs of water flow on MarsEarlier this week, NASA announced a press conference for Wednesday morning (US Pacific time; Thursday morning in eastern Australia) with "important news" about Mars. The news are: they have found evidence of liquid water on Mars. The important part is: not in the distant past, but in the last five years.

Two images of the same area of the planet taken by the Mars Global Surveyor in 1999 and 2005 (seen here) show changes that indicate a recent flow of liquid water on the surface; images of a different area show similar activity happening after mid-2002. The supposed flows of water left behind lightly-colored deposits, which are very rare on Mars (disturbances of the soil usually show the darker material that is underneath).

It is presumed that the water flowed from underground deposits, but it's not clear whether the water is permanently liquid (thus providing good conditions for underground habitats for local life-forms) or just becoming liquid for a short period and spurting out of the ground when that happens. When exposed to the thin atmosphere of Mars, liquid water doesn't last very long; it quickly becomes either solid ice (due to the low temperature) or vapour (due to the low pressure).

The Mars Global Surveyor recently stopped sending data and was declared lost, but it clearly brought very important information to Earth; analysis of its images will almost certainly bring more discoveries over the next years. And, of course, the discovery of the presence of liquid water on the planet, even temporarily, brings a boost to the idea of sending people there in the near future.

MRO images the Vikings

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Viking I from aboveThe Mars Reconnaissance Orbiter keeps sending great images of the surface of Mars; the latest offerings are pictures of the equipment of previous missions, now sitting on the planet. Opportunity had already posed for the cameras, and now Viking I (pictured), Viking II and Spirit join the family album. The Vikings have been in Mars since 1976, but all parts of the vehicles (heat shields, parachutes and the actual lander) are clearly visible in the pictures taken from above.

No word on the Beagle yet, and the MRO was'nt able to find Mars Express either, unfortunately. Anyway, I can't wait for Google Mars to incorporate the MRO high resolution images...

My bookmarks for this week

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Shared bookmarks for user wafonso

About this Archive

This page is an archive of entries from December 2006 listed from newest to oldest.

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