Archive for August, 2008

The Chemistry of Snow - by Christoper Boxe

Thursday, August 21st, 2008

This graphic illustrates the path of ozone-damaging molecules at Earth’s poles. Image credit: NASA-JPL

Remember the warning to beware of yellow snow? Well, what’s true in your backyard is true on a much larger scale too. (For those from warmer climates, yellow-tinted snow is a sign that a dog or other animal has recently “paid a visit.”)

Snow at Earth’s north and south poles can also be tainted. Certain molecules — ones that can eventually damage our protective ozone layer in the stratosphere, affect the air down in the troposphere where we live, and possibly contribute to climate change — are being deposited into the snow.

Just how is this happening? Start with the fact that air at lower latitudes circulates toward the poles. This air carries ozone-damaging molecules picked up in industrial, highly populated areas. Once over the poles, some of these molecules are deposited onto the snowpack, where they migrate to thin liquid films in snow. Once sunlight hits the snow, the light energy breaks down these molecules, which are then released back into the atmosphere, giving the area over the poles a double hit of ozone-damaging molecules.

Scientists are finding that snow has unique properties that make these chemical reactions happen much faster than we used to believe. We don’t fully understand why this is happening, but we know that the mixture of sun (an energy source) and snow bring about the release of these ozone-damaging molecules into the atmosphere much faster than in areas without snow.

Many of the polluting molecules that remain in the snow eventually get incorporated in the polar food chain. When the snow melts into the sea, the molecules may be ingested by sea creatures. Not all of them are unhealthy, but some of them are.

Why care about reactions going on in distant, frozen expanses at Earth’s poles? Those regions are a beacon of climate change, where we see chemical processes that may play a large role in the planet’s future.

It’s a Sure Bet - by Josh Willis

Wednesday, August 13th, 2008


My wife likes to gamble. She’s no high roller or anything, but give her a hundred dollars, a spare weekend and a room full of slot machines and she’s happy.

Not me, though. Somewhere along the way, I guess I took one too many math classes and betting against the house just isn’t much fun anymore.

But I understand why she likes it. It’s the ups and downs of gambling that are fun. You lose, lose, lose and then every once in a while you win a great big jackpot. Maybe you even win enough to make up for the last 30 or 40 bets you lost. But like any game in the casino, the odds are stacked against you. If you play long enough, you will eventually lose.

Global warming and climate change work in much the same way. Wait long enough and odds are, the Earth will be warmer. But will tomorrow be warmer than today? Who knows! There are plenty of things about the atmosphere and ocean that can’t be predicted. Over a period of days or weeks, we call these unpredictable changes “the weather.”

No one can predict the weather more than a few days in advance, any more than they can predict which slot the roulette ball will land in before the croupier spins it. Weather, like roulette, is essentially random.

But a little randomness doesn’t stop casino owners from taking your bet at the roulette table. They know the odds, and they know if enough bets are laid they will eventually come out ahead. Climate scientists know that, too.

Random events happen in the atmosphere and oceans all the time. Not just the weather, but things like El Nino, La Nina and huge volcanic eruptions can make the planet warm up or cool down for years at time. There could even be a few others that we haven’t discovered yet.

Still, for all its short-term ups and downs Earth’s average temperature has risen dramatically over the last one hundred years. That’s no accident. Like the house edge at the roulette table, human-made greenhouse gasses have tilted the odds in favor of a warming planet.

This graph shows Earth’s global temperature has been in an upward swing overall for more than 100 years. Image credit: Goddard Institue for Space Studies

Sometimes it’s easy to forget that fact when new science results come out. Like the recreational gambler, we often find it more fun to focus on the ups and downs: a short-term cooling period, a warm year during a big El Nino.

But for climate change and casino owners, it’s important to remember the big picture. The roulette player might win three or four bets in a row, but that doesn’t change the odds. Eventually the casino will win. Likewise, as long as humans continue to add carbon dioxide to the atmosphere, the planet will continue to warm.

So whenever people ask me about the latest warming or cooling in the climate record, I’m always reminded of my wife and her slot machines. By the end of the weekend her hundred dollars is almost always gone, but the thrill of the ups and downs kept her entertained for the entire time. “Did you win?” people ask. She always flashes her sly smile and says, “Sometimes!”

Looking for Earths Far From Home - by Tracy Drain

Monday, August 4th, 2008
What is Kepler?
photometer lowered into spacecraft
The photometer is lowered into the spacecraft in this picture. › Larger image

Kepler is a mission that is designed to find Earth-sized planets outside our solar system. Specifically, it will look for these rocky planets in the “habitable zone” near their stars — meaning at a distance where liquid water could exist on the surface.

Kepler will accomplish this by monitoring a large set of stars (approximately 100,000) and looking for the signature dip in brightness that indicates that a planet has crossed between the spacecraft and the star. The instrument that detects this dip is called a photometer — literally, a “light meter.” It is basically a large telescope that funnels the light from the stars onto a CCD array (similar to the ones used in digital cameras).

By surveying such a large number of stars using this “transit” method, Kepler will be able to determine the frequency of Earth-sized (and larger) planets around a wide variety of stars.

What do I think is cool about this mission?

I love the fact that the Kepler approach - looking for the dips in stellar brightness that occur when a planet passes between the photometer and a star - is so straightforward. It is such a wonderfully simple way to look for planets! Of course in practice, there are plenty of complicating factors that make this a challenging mission to execute. The change in brightness that we are looking for is very small (on the order of 0.01 percent). To make sure we can detect that, we have to carefully control noise in the system - things like electronic noise from reading out the CCDs, smear from tiny motions of the spacecraft, etc. These and other aspects of the mission have provided plenty of challenges to keep things interesting for the design team.

One of my favorite things about the Kepler mission is that the patch of sky we will be surveying is near a particular group of highly recognizable constellations. The stars Kepler will look at are in the area of what is known as the Summer Triangle, a group of constellations - Aquila, Cygnus and Lyra - that are overhead at midnight when viewed from northern latitudes in the summer months. When the scientist team starts identifying planets in our field of view, anyone will be able to go outside, point towards the Summer Triangle and say “they’ve just discovered a planet over there.” To me, there is something about that which will make the discoveries that much more personal.

photometer lowered into spacecraft
This image shows the Milky Way region of the sky where the Kepler photometer will be pointing. Image credit: Carter Roberts, Eastbay Astronomical Society, Oakland, Calif. › Larger image

I am also a huge sci-fi fan and I have always been particularly fascinated by books and movies about how humans might some day colonize other worlds in the galaxy. I think it is fantastic to get to work on a mission that will be looking for planets outside our solar system that are Earth-sized and in a range around their stars that could be habitable; places where such colonization could one day take place… I can’t wait to see what we find!

What do I do?

I am a member of the Project System Engineering Team at JPL. This team is responsible for a wide variety of tasks on Kepler, aimed at ensuring the project meets the driving scientific and technological objectives. This often involves checking that the interfaces between the different elements of the project work smoothly. For example, one of our responsibilities is to conduct end-to-end tests of the mission’s information system. In this test, we check to make sure that the right commands are being generated to collect data, data is collected using spacecraft hardware, and then the data flows correctly through the ground data system. This lets us verify that the entire data flow chain functions as it should before we launch.

My particular focus has been ensuring that we work out all of the details associated with executing each of the mission phases (the launch phase, the on-orbit checkout period that we call the commissioning phase, and the main data-gathering portion of the mission, which is the science phase). I work closely with my colleagues at NASA Ames, Ball Aerospace and JPL to identify and resolve open issues associated with planning for, testing and eventually executing the activities associated with these phases.

What is happening on the project right now?

This animation shows how Kepler will work.

The project is in what is known as the Assembly, Test and Launch Operations phase. Right now, the assembled spacecraft and instrument (known collectively as the flight system) is in the middle of the environmental testing campaign at Ball. This involves many hours of running the flight system and monitoring its performance while exposing it to the types of temperatures, pressures and other conditions that it will see in space. The system that will collect and distribute the data is undergoing integrated testing as well, with teams of people working to push test data through all of the various ground interfaces. The operations team — the people who will be responsible for generating and testing commands, monitoring the health and safety of the spacecraft and ensuring that data is collected from it by the Deep Space Network — are undergoing training and getting ready for upcoming mission phase rehearsals that we call “operational readiness tests.” Even though we are still several months away from launch, it is a very busy time on the project!

Who is involved?

The principle investigator and the science office that will lead the scientific data analysis are at the NASA Ames Research Center in Mountain View, Calif. The spacecraft and photometer were built at Ball Aerospace & Technologies Corporation in Boulder, Colo. The mission operations center is located at the Laboratory for Atmospheric and Space Physics at the University of Colorado at Boulder. The mission is managed here at the Jet Propulsion Laboratory in Pasadena, Calif.

TEGA Status and More - by Deborah Bass

Friday, August 1st, 2008

This view combines more than 400 images taken during the first several weeks after NASA's Phoenix Mars Lander arrived on an arctic plain at 62.22 degrees north latitude, 234.25 degrees east longitude on Mars.
This view combines more than 400 images taken during the first several weeks after
NASA’s Phoenix Mars Lander arrived on an arctic plain at 62.22 degrees north latitude,
234.25 degrees east longitude on Mars.
› Full image and caption

Thanks to all those who posted comments! I’m glad to see that there is
so much interest in the Phoenix mission! I wanted to address a few key

First off, some staff from the Mars Science Laboratory project
will be writing blog entries, so please hold your questions about that mission until
the end of summer, when those blogs begin!

Phoenix’s Thermal and Evolved-Gas Analyzer, or TEGA, has given the team some
head-scratchers, and those challenges continue. In my last blog I talked about lumpy
soil, sprinkling and delivery mechanisms. TEGA has been using a method to agitate its
cells to help move the soil down from the collection area into the oven as well. Well, it
turns out there was a short circuit in a TEGA cell number four when we used the agitator
on that cell in June. We used that same agitator for repeated periods of many minutes
each time while we were getting the first soil sample into TEGA. Project engineers
determined the likely cause was running the screen-agitator longer than we ever had done
in pre-launch testing. Running the circuit for such a long time caused some wire
insulation to get too warm, causing a short. That short in itself did not cause or
threaten any problem with operating TEGA, just on the “grounded” portion of the circuit.
It was on the return part of the circuit, between where the current does its work and the
ground connection. And then that short apparently healed itself when doors for cell
number zero were opened on July 19! However, the occurrence of any short raised concerns
that another short circuit might possibly occur, and if it did, it might be a more
harmful one. That concern still exists, and has prompted at least two precautions — a
decision to change sampling strategy to treat each TEGA sample as if it could be the
last, and an operational rule to avoid running a screen-agitation for more than three
minutes without a cool-down period before resuming.

Trying to get samples into the chemistry experiment was a big topic during development. When Peter Smith proposed to send Phoenix to the Martian arctic, the intention was to use as many already-developed pieces as possible. New methods of delivering material to the chemistry experiments on the lander deck had to be simple, because the original design was to use the scoop to dump soil. However, based on pre-launch testing, the original method of scraping/scooping the soil to generate a sample didn’t appear to work on ground that is frozen so hard that the ice and soil behaves like cement! The Phoenix team has been doing many tests to ensure that the alternative method, using a little Dremel-like tool called the rasp, works. These tests were done on analogs of extra-hard Martian soil, but there is still nothing like testing with the real stuff on Mars. The Phoenix team had established that the rasp will acquire enough icy soil to deliver a proper sample to TEGA. Those on-Mars tests have taken a long time, as expected. Mars continues to amaze the science and engineering team - the Martian soil is behaving unlike any sample the team used in practice back on Earth! The exciting news is that the team was able to get a sample with a bit of ice into TEGA after all!

Another item came up regarding better ways to clear off the ice table. I’ll tell you that the Phoenix development team wrestled with this topic for quite some time. Field studies show that a brush is the best way to remove loose soil from a region a geologist wishes to sample. The problem of course, is that then the brush gets dirty! The ability to clean the brush for further use becomes the problem. The soil on Mars is very, very sticky due to small particle sizes, salts and ice that appear to be acting as cements, and electrostatic properties that cause dust-sized particles to be charged and stick to each other that way too. The team could not come up with a reasonable, relatively inexpensive brush/cleaning mechanism in the short development cycle that the Phoenix mission undertook. (Remember that the mission was only approved in August 2003!) The notion of using the scraping blade on the robotic arm was deemed the most expedient, least costly way to clean surfaces.

Hope this answers some of your questions. Thanks for all of your interest!