On Wednesday, the Phoenix Mars probe successfully delivered a scoop of icy martian soil to its chemistry lab. Previous attempts had failed because the soil proved stickier than expected. Although all indications were that the white stuff Phoenix uncovered was water ice, Phoenix's lab results now confirm it. William Boynton, lead scientist for the Thermal and Evolved-Gas Analyzer said, "We have water".
Showing posts with label space. Show all posts
Showing posts with label space. Show all posts
Thursday, July 31, 2008
"We have water"
Friday, June 20, 2008
Ice on Mars!!
On Sunday, I posted that the Phoenix probe uncovered a white substance which might be frozen water, though it could have been a salt. Turns out it IS water. The evidence? Some of it disappeared by the time the next picture was taken--it must have evaporated. You can see that white chunks in the Sol 20 picture have disappeared within 4 Martian days. Salt doesn't do that. So Phoenix has found water ice on Mars!
As I said Sunday, this is the first contact with alien water. The probe will now look for evidence of the building blocks for life.
Sunday, June 15, 2008
Mars Phoenix Probe Hits White Gold?
The Mars Phoenix probe, which touched down on the north polar region of Mars twenty days ago, has begun digging with its robotic arm. Dirt from the first scoop was "stickier" than expected perhaps due to moisture? Where would moisture come from on that dry world? Scientists chose the polar landing site because orbital imaging indicated that there is ice underneath the surface. But could it be this close to the surface? Pictured above is the trench that Phoenix has enlarged. You can see light patches in the trenches. They are either streaks of some salt, or water ice--white gold, if you will. If turns out to be ice, it will be the first alien water we've ever had a chance to study. We should find out very soon. [It IS ice!]
Monday, May 26, 2008
Mars Phoenix Probe Sees Permafrost Pattern
The Mars Phoenix probe has just landed safely on the polar region of Mars. The terrain exhibits "polygonal cracking"—it looks like it has been shaped by repeated melting and freezing of ice below the surface. If Phoenix's digging arm can detect that ice, it would be the first contact with alien water.
Friday, February 22, 2008
Spy Satellite and Space Junk
The US military just destroyed a spy satellite with a missile strike. Let's forget, how unlikely it was that the satellite would have hit near anyone if they had just let it reenter the atmosphere on its own. Let's also forget that this strike was a simple way to make a flawed missile defense system look good (I am sure that the path of the satellite was much more predictable than any real incoming ordinance). Let's also forget about the worry that the strike could contribute to the militarization of space. What I want to concentrate on is the possible effect of all the junk that the explosion produced, and the resulting danger to satellites and astronauts.The photo above shows about 10,000 objects of baseball size or larger in low Earth orbit tracked by NASA. There are perhaps 600,000 objects larger than a centimeter which are too small to track. Now if that doesn't sound worrying to you, note that objects in such orbits move around the Earth at more than 17,000 mph (27,000 kph), and the energy of an object goes as the velocity squared. That means being slammed with a 1 kg object at orbital speed involves as much energy as a 60,000 kg 18-wheeled truck crashing into you at 70 mph (113 kph), except that in the former case the energy is concentrated into a much smaller object. This is what being hit by a tiny object going 17,000 mph looks like:
So how many pieces of space junk did the spy satellite strike create? Well, it is estimated that the Chinese destruction of one of their satellites in 2007 increased the amount of space junk by about 30%. [It is fair to note, as Rampant Clam's Comment points out, that the Chinese satellite was in a more stable orbit than the US satellite, so what the Chinese did was far worse because it created much more long-lived debris.]
Sunday, January 27, 2008
Obama Endorsements January 14-28
My most popular post so far has been Barack Obama Endorsements [January 4-14], which I posted two weeks ago. [For a current list, see Running List of Obama Endorsements.] Since that time, there have been several high profile endorsements. Most moving of all was the stunning endorsement from Caroline Kennedy, daughter of JFK, delivered through a New York Times Op Ed piece entitled A President Like My Father. She ends,
"I have never had a president who inspired me the way people tell me that my father inspired them. But for the first time, I believe I have found the man who could be that president - not just for me, but for a new generation of Americans."
[John F. Kennedy speech at Rice University on 12 September 1962, a year after the space program was ramped up, and less than seven years before the moon landing.]
Of course, Obama does not have plans to take us to the Moon, and as I said, space is best explored by robots for now. But I believe that Barack Obama can inspire us and lead us to tackle the problems of our time.
Here is a list of the individuals above:
- Senator Edward Kennedy (of Massachusetts, brother of JFK)
- Caroline Kennedy (daughter of JFK)
- Senator Patrick Leahy (of Vermont)
- Former Senator Jean Carnahan (of Missouri)
- Congressman Rick Boucher (of Virginia)
Here are some recent newspaper endorsements of Obama:
- San Francisco Chronicle
- San Jose Mercury News
- Modesto Bee
- Santa Barbara Independent
- New York Observer
- St. Louis Post-Dispatch
- Arizona Republic
- Philadelphia Inquirer
- Chicago Tribune
- Seattle Times
- Rocky Mountain News
Saturday, January 12, 2008
More on Why Asteroid Will Miss Mars
As you can see, the dots are bunched around the most probable value and taper off in either direction—in the same way that the the area under a bell curve decreases away from the center. s, the distance from the blue line to Mars divided by the size of the error, is 3.7, giving a probability of 10,000:1.
Here is what the asteroid figure looked like two weeks ago:
Notice that the scale here is 500,000 km, so this is zoomed out by a factor of 5 from the 9 January picture. Two things have happened in the fortnight. First, the position of the blue line has changed a little. More importantly, the size of the error was a lot bigger two weeks ago. Back then the error was large enough so that the distance from the blue line to Mars divided by the error was only 2.2, giving a probability of 25:1.So the probability changed from 25:1 to 10,000:1 over the last two weeks mainly because the error in the path decreased, making s increase (again, s is the distance from the blue line to Mars divided by the error, and it is also the position on the bell curve of the previous post).
Friday, January 11, 2008
Why Asteroid Will Miss Mars
Last month, it was reported that a very small asteroid had a 1-in-75 chance of hitting Mars, which was very exciting. It would be awesome to see the effects of such a collision. Then the number was 1-in-25, which was even more exciting. Now the number has dropped to 1-in-10,000, so it is very unlikely to happen. How could the numbers change that much?
[see also next post, More on Why Asteroid Will Miss Mars]
Suppose it was your job to calculate the probability the asteroid would hit. You would take the most accurate measurements of the asteroid, extrapolate its position, and come up with your best estimate of the path for the asteroid. Now there would be some uncertainty in your estimate for the path. Let's call s the distance of closest approach to Mars of your best guess for the path. The plot of probabilities is given by this bell curve (also called a Gaussian curve):
If you calculated that s=0, that the most likely path just grazes the surface of Mars, then all paths to the right of s=0 would hit Mars, and you'd say that the probability of hitting was 1/2 (half the area under the curve is to the right of s=0). If you calculated that s=2.2 (which they did in December), then only paths more than 2.2 standard deviations from the most likely path would hit Mars, a chance of 75 to 1 (less than 2.1%). And if your calculation shifted just a little, so that s=3.7 (the value now), then only the paths more than 3.7 standard deviations from the most likely path would hit Mars, a chance of 10,000 to 1. It takes only a little shift out on a bell curve to make the probability plummet.
And so a small refinement in measurements of the asteroid positions made the impact probability... crash.
[Notice that I did not put any units on s, because s is really distance/error-in-path-estimation, so that s=1 corresponds to whatever 1 standard deviation is in this case. We don't need the actual distances in km because we are taking a ratio.]
[image from here, arrows and text added by me (feel free to use)]
[confidence: likely, my qualifications: informed]
Sunday, December 16, 2007
"One small step for man..."
The explorer was getting low on food. He was in a desolate landscape of sand and rocks. His lame leg tore a ragged trench as he doggedly dragged it through the sand. How long could he last? Would he find the treasure, or would he expire first? Then he came upon it without warning. Ironically, it had been uncovered by his lame foot. There glistening in the sunlight was a streak of "white gold", evidence for an ancient hot spring on Mars.
The explorer is 4'11" tall, weighs 384 lbs, and rides on six wheels.
It is the Mars Rover Spirit. It gets its "food" from the sun. As the Martian sand builds up on its solar panels, less sunlight get through, and it "starves". At one point recently, a lucky gust of wind cleared its panels, but now they are dusty again and Mission Managers are unsure whether Spirit will make it through the cold dim Martian winter. One of Spirit's six wheels stopped turning in 2006, so they have had to drive it backwards through the sand since then. The "lame leg" digs a trench wherever it goes. It just happened to uncover a patch of white silica, the stuff of window glass.
The NASA Press Release states
"It could have come from either a hot-spring environment or an environment called a fumarole, in which acidic steam rises through cracks. On Earth, both of these types of settings teem with microbial life."
This was originally announced in May of 2007, but the conclusion has been bolstered by the finding that a rock called "Innocent Bystander" has an interior rich in silica and is probably thus a siliceous sinter.
While I am fascinated with these hints that ancient Mars may have been more hospitable to life, that's not what I wanted to stress in this post. I anthropomorphized Spirit to make a point. We respond viscerally to humans meeting challenges. (Actually, the public was quite interested in the Mars rovers when they landed, which surprised me. But that interest has faded.) If there were a human whose survival on Mars was in doubt, it would be the top story on every news outlet (and rightly so). If a human had dug up the silica, we'd be hearing all about her personal history and idiosyncrasies.
Humans are also much more adept than a robot in a setting, like Mars, where autonomous actions are required. A human could probably do the work the rovers have performed in a few days.
BUT, human space travel is very expensive. It would cost many, many more times the rover program to get a human to and from Mars (perhaps as much as a few months of the Iraq war). When the human part of the space program is expanded, other programs suffer, and there is often less science done.
Further, robotic vehicles are becoming more and more sophisticated. They may be all we need to accomplish our scientific goals.
So, until we are willing to commit the resources for both an intensive robotic science program and an expensive human space flight program, I think we should concentrate on sending robots, not humans.
[confidence level: likely, my qualifications: informed]
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