Posts Tagged ‘Universe’

Alien Vs. Editor: Life As We May (or May Not) Know It

Monday, April 18th, 2011

By Steve Edberg

Alien vs. Editor is a forum for questions and answers about extrasolar planets and NASA’s search for life beyond our solar system. Leave your questions for author Steve Edberg and read more on the PlanetQuest website.

Tubeworms that grow near the boundary where hot vent fluid mixes with cold seawater on the ocean floor are an example of extremophiles that broaden our perspective on where to look for life. Image credit: Nicolle Rager Fuller, National Science Foundation

A reader’s question (paraphrased): Why do astronomers assume there have to be conditions similar to Earth in order for life to exist? Who are we to define what life looks like and how would we know what we’re looking at if we really don’t know what we are looking for?

This has been a recurring question over the years, and I don’t think anyone interested in finding extraterrestrial life would dispute those thoughts. The problem is that we aren’t as clever as Mother Nature, so we don’t know what else to look for. More practically, we don’t know what other conditions to look for beyond those we are familiar with.

Science fiction writers have used their imaginations to propose other forms of life. Sir Fred Hoyle (an astronomer) wrote a novel titled “The Black Cloud,” (SPOILER/GIVEAWAY ALERT!! SKIP THE REST OF THIS SENTENCE IF YOU THINK YOU WILL READ THE BOOK) about a self-propelling interstellar cloud that came to orbit the sun to acquire energy (it stopped for lunch!) before moving on.

On the TV shows “Star Trek” and “Star Trek: The Next Generation,” the screenwriters came up with at least two forms of life that were completely novel. Naturally enough, the shows involving them were about recognizing that they were life and how to deal with it. The one on “Star Trek” was about rock-beings that tunneled through an asteroid or planet. The other, on “Star Trek TNG,” was about “nanites,” microscopic silicon crystals that were hive-like beings communicating among themselves electrically and with electromagnetic waves with the crew of Enterprise D.

These are three examples of potential life forms far different from what we are familiar with. But knowing what to look for and where is a long step from the presentation of these ideas in science fiction media.

Before the Viking landings on Mars in the 1970s, Carl Sagan gave talks about the life-detecting instruments aboard the landers, which were designed to detect life as we know it. He also mentioned that there was a camera aboard so that we could see any “silicon-based giraffes that might walk by,” so even then scientists were thinking about possible, unfamiliar forms of life.

The strategy being followed is to look for evidence of extraterrestrial life, as we recognize life, now, rather than wait until we figure out all the possibilities. Scientists study and search for new examples of “extremophiles” that live in extreme conditions compared to what most of life on Earth lives in, in order to broaden our perspective on where to look for life.

There are also radio and optical searches for evidence of extraterrestrial intelligence living (by whatever chemical process) on planets orbiting other stars that might be announcing their presence. And I recently heard that there is a meeting planned to consider what else we might look for in this arena, considering that the era of our radio transmissions out to the galaxy (TV and radio) could be coming to an end as we use more cable and fiber communications here on Earth.

Rocks and Stars with Amy: This Year I Saw the Universe

Tuesday, February 1st, 2011

By Amy Mainzer

Rocks and Stars with Amy

With WISE, I roamed the skies — seeing everything from the closest asteroids to the most distant galaxies. When I was a kid, maybe 6 or 7, I remember reading the encyclopedia about Andromeda, Mars and Jupiter. After that, I spent a lot of my free time (and a fair amount of gym class) wishing that I could be “out there” exploring the stars, imagining what it must be like to get close to a black hole or the lonely, cold surface of a moon. Fast-forwarding several decades, I’ve just spent a tremendously satisfying and delightful year using some of our most sophisticated technology to see “out there” for real. It’s pretty cool when your childhood dreams come true!

Today, the operations team sent the command to kill the survey sequence and put WISE into a deep sleep. While I’m sad to see the survey stop, the real voyage of discovery is just getting started as we unpack the treasures that our spacecraft beamed back to us. Although I’m going to miss waking up to see a new slew of pictures fresh from outer space, what I’ve looked at so far is only a tiny fraction of the millions of images we’ve garnered. My colleagues and I are working nonstop now to begin the decades-long process of interpreting the data. But I can already say for certain that we’re learning that the universe is a weirder, more wonderful place than any science fiction I’ve ever read. If I could go back in time to when I was kid, I’d tell myself not to worry and to hang in there through the tough parts — it was all worth it.

A cast of hundreds, maybe thousands, of people have worked on WISE and deserve far more credit than they get. The scientists will swoop in and write papers, but all those results are squarely due to the brilliance, stubborn persistence and imagination of the technicians, managers, engineers of all stripes (experts in everything from the optical properties of strange materials to the orbital perturbations of the planets), and administrative staff who make sure we get home safely from our travels. Although we may not be able to fly people around the galaxy yet, one thing Star Trek got right is the spirit of camaraderie and teamwork that makes projects like WISE go. For the opportunity to explore the universe with such fine friends and teammates, I am truly grateful.

Rocks and Stars with Amy: Milestones

Tuesday, July 20th, 2010
Rocks and Stars with Amy
By Amy Mainzer

It’s hard to believe that we’ve just crossed the six-month mark on WISE — seems like just yesterday when we were all up at Vandenberg Air Force Base, near Santa Barbara, shivering in the cold at night while watching the countdown clock. But the time is flying (literally!) as WISE whips by over our heads. We’re analyzing data ferociously now, trying to get the images and the data ready for the public release next May. Even though the mission’s lifetime is short, we’ve gotten into a semblance of a routine. We receive and process images of stars, galaxies and other objects taken by the spacecraft every day, and we’re running our asteroid-hunting routine on Mondays and Thursdays. We’ve got a small army (well, okay, three — but they do the work of a small army!) of extremely talented students who are helping us verify and validate the asteroid detections, as well as hunt for new comets in the data. Plus, there is an unseen, yet powerful, cadre of observers out there all over the world following up our observations.

asteroids and comets detected by WISEThis plot shows asteroids and comets observed by NASA’s Wide-field Infrared Survey Explorer, or WISE. Image credit: NASA/JPL-Caltech/ULCA/JHU   |   ›See related video

And so it’s come to pass that we’ve achieved some milestones. We completed our first survey of the entire sky on July 17 — and we just discovered our 100th new near-Earth object! That’s out of the approximately 25,000 new asteroids we’ve discovered in total so far; most of these hang out in the main belt between Mars and Jupiter and never get anywhere near Earth’s orbit. These new discoveries will allow us to conduct an accurate census of both the near-Earth and main belt asteroid populations. We’re really busy chewing on the data right now and calculating what it all means.

Because it’s so short, this mission reminds me a little bit of what the first days of college felt like — a tidal wave of new ideas, new sights and new thoughts. The pace of learning has been incredibly quick, whether I’m trying to get up to speed on asteroid evolution theories or tinkering with the software we use to write papers.

Speaking of papers, we’re in the process of preparing to submit several to science journals; in fact, I’ve already submitted one. The gold standard of science, of course, is the peer-review process. We submit our paper to a journal, and the scientific editor assigns another scientist who is an expert in the field but not involved in the project (and who usually remains anonymous) to read it and offer comments. The referee’s job is to “kick the tires,” so to speak, and ask tough questions about the work to make sure it’s sound. We get a chance to respond, and the referee gets a chance to respond to our responses, and then when everybody’s convinced the results are right, the paper is accepted and can be published. So stay tuned — we should have some of the first papers done soon telling us what these milestones mean for asteroid science.

› Read more from “Rocks and Stars with Amy”

Super Swooper: Cassini wraps up its lowest pass through Titan atmosphere

Monday, June 21st, 2010
Julie Webster
Julie Webster

On Sunday evening, my eyes were glued to eight windows on my computer screen, watching data pop up every few seconds. NASA’s Cassini spacecraft was making its lowest swing through the atmosphere of Saturn’s moon Titan and I was on the edge of my seat. Trina Ray, a Titan orbiter science team co-chair, was keeping me company. Five other members of my team were also at JPL. Between us, we were keeping an eye on about 2,000 data channels.

One of the 34-meter antennas at the Deep Space Network’s Goldstone complex, DSS-24, was pointed at Saturn and listening for the signal that was expected to be here in just a few minutes. The data would be arriving at my computer as quickly as they could be sent back to Earth, though there was an agonizing hour-and-18-minute delay because of the distance the data had to travel. (We call this flyby T70, but it is actually Cassini’s 71st flyby of Titan.)

It was a nervous time for me — the previous night we had been at JPL to send some other real-time commands to the spacecraft when an alarm came in indicating that the magnetometer, the prime instrument taking data for the T70 flyby, needed a reset. Fortunately, the controller on duty immediately called the magnetometer instrument operations team lead in England. Within 90 minutes, the commands were on their way to do a computer reset and clear the alarm. At 2 a.m. Pacific time on Sunday, we got the email indicating all was well and the magnetometer was ready for the Titan closest approach.

So here we were, past one hurdle, hoping nothing else would come up. We had run hundreds of simulations over the past three-and-a-half years, so I knew we had done everything we could think to do. We did more training for this event than anything else we had done since we dropped off the Huygens probe in January 2005 for a descent through the moon’s hazy atmosphere.

Right on time, at 7:26 p.m., the Deep Space Network locked on the spacecraft downlink, a good start. I was focused on the data for spacecraft pointing. As long as we stayed within an eighth of a degree of the expected pointing, everything would be fine. At 7:45 p.m., we got the data from closest approach, a mere 880 kilometers (547 miles) in altitude. Over the vocabox, a cross between a telephone and walkie-talkie, the attitude control team reported that the thrusters were firing about twice as much as we expected. The Titan atmosphere appeared to be a little thicker than we expected, even though we had fed about 40 previous low Titan flybys by Cassini and the descent data from Huygens into our modeling.

But spacecraft control was right on the money, keeping the pointing within our predicted limits. Even with the extra thrusting, we stayed well within our safety margin.

At 7:53 p.m., the spacecraft turned away to go to the next observation. I let out a sigh of relief, happy that everything during closest approach had gone just as we planned. Five attitude control guys crowded into my office with smiles on their faces. Trina and I were marveling at what a wonderful spacecraft we have to work with. Another first for the Cassini mission!

Now, as Trina says, we have to finish the job by returning all the great science data. We have data playbacks today at two different Deep Space Network stations to make sure we have - as we say here - both belts and suspenders. Engineers will also go back to analyze the data with the scientists to see just how dense the Titan atmosphere turned out to be at our flyby altitude.

But last night, at least, my team and I went home happy!

Cassini to Swing Low Into Titan’s Atmosphere

Thursday, June 17th, 2010
César Bertucci
César Bertucci

This weekend, Cassini will embark on an exciting mission: trying to establish if Titan, Saturn’s largest moon, possesses a magnetic field of its own. This is important for understanding the moon’s interior and geochemical evolution.

For Titan scientists, this is one of the most anticipated flybys of the whole mission. We want to get as close to the surface with our magnetometer as possible for a one-of-a-kind scan of the moon. Magnetometer team scientists (including me) have a reputation for pushing the lower limits. In a world of infinite possibilities, we would have liked many flybys at 800 kilometers. But we went back and forth a lot with the engineers, who have to ensure the safety of the spacecraft and fuel reserves. We agreed on one flyby at 880 kilometers (547 miles) and both sides were happy.

Artist's concept of Cassini's Titan flyby
Cassini flies to within 880 kilometers (547 miles) of Titan’s surface during its 71st flyby of Titan, known as “T70,” the lowest in the entire mission. Image credit: NASA/JPL/Space Science Institute
› Full image and caption

Flying at this low altitude will mark the first time Cassini will be below the moon’s ionosphere, a shell of electrons and other charged particles that make up the upper part of the atmosphere. As a result, the spacecraft will find itself in a region almost entirely shielded from Saturn’s magnetic field and will be able to detect any magnetic signature originating from within Titan.

Titan orbits within the confines of the magnetic bubble around Saturn and is permanently exposed to the planet’s magnetic disturbances. Previous measurements by NASA’s Voyager spacecraft and Cassini at altitudes above 950 kilometers (590 miles) have shown that Titan does not possess an appreciable magnetic field capable of counterbalancing Saturn’s. However, this does not imply that Titan’s field is zero. We’d like to know what the internal field might be, no matter how small.

The internal structure of Titan can be probed remotely from its gravitational field or its magnetic properties. Planets with a magnetic field — like Titan’s parent Saturn or our Earth — are believed to generate their global-scale magnetic fields from a mechanism called a dynamo. Dynamo magnetic fields are generated from currents in a molten core where charge-conducting materials such as metals are flowing around each other and also undergoing other stresses because of the planet’s rotation.

We might not find a magnetic field at all. A positive detection of an internal magnetic field from Titan could imply one of the following:

a) Titan’s interior still bears enough energy to sustain a dynamo.
b) Titan’s interior is “cold” (and therefore has no dynamo), but its crust is magnetized in a similar way as Mars’ crust. If this is the case, we should find out how this magnetization took place.
c) Something under the surface of Titan got charged temporarily by Saturn’s magnetic field before this Cassini flyby. While I said earlier that the ionosphere shields the Titan atmosphere from Saturn’s magnetic bubble, the ionosphere is only an active shield when the moon is exposed to sunlight. During part of its orbit around the planet, Titan is in the dark and magnetic field lines from Saturn can reach the Titan surface. A temporary magnetic field can be created if there is a conducting layer, like an ocean, on or below the moon’s crust.

Once Cassini leaves Titan, the spacecraft will perform a series of rolls to fine-calibrate its magnetometer in order to assess T70 measurements with the highest precision. We’re looking forward to poring through the data coming down, especially after all the negotiations we had to make for them!

Rocks and Stars with Amy: The Golden Ticket

Friday, January 29th, 2010

By Amy Mainzer

Rocks and Stars with Amy

We have discovered our first new near-Earth asteroid with WISE. Our first “golden ticket” is now known as 2010 AB78. It’s an asteroid that is roughly 1 kilometer [about .6 miles] in diameter, so it’s fairly large. The most interesting thing about it so far is that we thought we knew of about 85 percent of all the asteroids 1 kilometer and larger, so finding a big one like this is a little unusual. Of course, unlike Charlie and his chocolate bars, finding the golden ticket wasn’t a matter of luck, but a meticulous search process more like a busy assembly line.

Near-Earth objects are asteroids and comets with orbits that get close to Earth’s orbit. That doesn’t mean they are going to hit the Earth, of course. It’s sort of like driving on a busy street; just because there are a lot of cars zipping by on either side of you, it doesn’t necessarily mean your car is going to hit one. The cars would have to be at the same place at the same time for that to happen. So even though the paths each car has traveled might get close, there is no collision.

WISE finds asteroids by using a sophisticated piece of software called the WISE Moving Object Processing System, or WMOPS. When we first get a set of images from WISE, we have software that automatically searches the images for all the sources in them, be they stars, galaxies or asteroids. The software records their positions and how bright they are. WMOPS goes into that source list and figures out which sources are moving compared to the fixed stars and galaxies in each frame. Then, it figures out which sources are actually the same object — just observed at different times. So it’s a pretty smart piece of code. The whole system has to be highly automated, since when the WISE survey is done, the source catalog will contain several hundred million sources! You can imagine that trying to sort through all of these to find individual objects would be very challenging without a nifty program like WMOPS.

Our newest addition to the approximately 6,600 near-Earth Asteroids that are currently known is shown in this new image:

artist's concept of the WISE space telescope
The red dot at the center of this image is the first near-Earth asteroid discovered by NASA’s Wide-Field Infrared Survey Explorer, or WISE — an all-sky mapping infrared mission designed to see all sorts of cosmic objects. Image credit: NASA/JPL-Caltech/UCLA
› Full image and caption

2010 AB78 shows up like a glowing red ember at the center of the image, because it’s glowing brightly in infrared light with a wavelength of 12 microns, which is about 20 times redder than your eye can see. The stars appear blue, because they’re much hotter, and they emit proportionally less of their energy at these long wavelengths. The color that the asteroids appear to WISE is an important feature we use to distinguish them from other stars and galaxies, in addition to their motion.

With this first asteroid discovery, we are flexing our muscles in preparation for the heavy lifting we’re about to start.

Rocks and Stars with Amy: It’s Time to Go

Friday, December 11th, 2009

By Amy Mainzer

Rocks and Stars with Amy

Now that we are just days from launch (wow!), the team is making final decisions and preparations. We’ve just held our Flight Readiness Review, at which the final commitment to launch was made by NASA, the United Launch Alliance (the rocket folks) and the WISE project. It turns out that fueling our Delta II rocket’s second stage engine is an irreversible process — once we fuel the second stage, we have 34 days to launch the rocket. If we don’t launch within 34 days of fueling it, we have to replace the second stage completely — and that would mean taking WISE off the rocket. So we needed to be really sure that we were “go for launch” before we decided to fuel up the second stage. That is now done, and we are in the process of putting the final finishing touches on cooling down our solid hydrogen tanks.

These last few weeks and days before launch require a lot of flexibility of the team, since the schedule can change on a dime. There are about a million things having nothing to do with the launch vehicle or the spacecraft that can delay a launch — winds, too much fog, too many clouds, lightning and even something as mundane as a fishing boat or aircraft straying into the “keepout” zone that’s established around the launch site. You would think that the prospect of running into a giant, 330,000-pound rocket loaded with fuel would be enough to make people move out of the way, but sometimes they don’t seem to get the message! Any of these items is enough to scrub a launch attempt.

But that’s why we’ve built in the ability to make two consecutive launch attempts with WISE, separated by 24 hours. We get two tries. After that, our tank full of frozen hydrogen starts to warm up too much, and it takes two days for us to cool it back down. To keep the tank of frozen hydrogen a frosty 7 degrees above absolute zero (minus 447 Fahrenheit), we circulate an even colder refrigerant, liquid helium, around the outside of the tank. But the process of re-cooling takes two days; we have to hook all the hoses back up, cool everything down, then disconnect the hoses again before the next launch attempt.

So we have to be flexible. We’ve all put our lives on hold for the duration, since we have to be ready for anything that happens. Meanwhile, I’ve frantically tried to take care of stuff like cleaning the house and laying in supplies, because once WISE launches, things will go into overdrive. Needless to say, our families have all been very patient with us!

Rocks and Stars with Amy: Hi Ho, Hi Ho, It’s Into Space We Go

Thursday, November 5th, 2009

By Amy Mainzer

Rocks and Stars with Amy

With WISE a mere month away from liftoff, it’s probably a little late to be asking why we need to send it into space. But it’s worth taking the time to explain why we go to all the trouble of sending something up on a rocket. While it’s really cool to go into space, we’re not just sending WISE up there for the fun of it. In this case, there’s no other reasonable way to accomplish the mission’s science goals: surveying the entire sky in infrared, finding the nearest star to our sun, and finding the most luminous galaxy in the universe. We can’t do this from the ground.

artist concept of WISEIt turns out that the main culprit that drives us into space and into an orbit more than 500 kilometers (about 360 miles) above the Earth’s surface is our atmosphere. As wonderful as our atmosphere is for life on Earth, it wreaks havoc on astronomical images in many ways. For one, shifting pockets of warm and cool air drifting above a telescope — or a human observer– cause stars to twinkle. While pretty, this twinkling makes it difficult to get a good measurement of a star’s true brightness (or, in astronomical terms, its “photometry”). The twinkling also reduces the telescope’s sensitivity and resolution by enlarging the images it produces, making them blurrier and less sharp. This is true for all kinds of telescopes not just infrared ones.

Secondly, the atmosphere acts like a sponge at many wavelengths, soaking up light from the stars so that it never reaches the ground at all. Everybody’s seen a rainbow at one time or another, and that range of colors — from violet to red — spans the maximum range of wavelengths that our eyes can see. But that is only a small fraction of the entire spectrum of light that’s really out there in the universe. Our sun puts out most of its radiation in visible light, and most of that visible light makes it through our atmosphere to the ground. However, our atmosphere is only partially transparent to infrared wavelengths. Filled with water vapor, carbon dioxide, and methane, our atmosphere absorbs almost all infrared light, so most of the infrared light emitted by distant stars, asteroids, and planets doesn’t make it to observers on the ground. These molecules grab infrared light and trap it, preventing it from passing through the atmosphere (which is why they are called greenhouse gases). To see anything at all in most infrared colors, we have to get entirely above the Earth’s atmosphere.

The final problem posed by our atmosphere for infrared astronomers is that it — and the Earth itself — is warm. Infrared light is characteristically emitted by room-temperature objects. Objects like you and I glow brightly in infrared light, and so does the Earth and its atmosphere. If you could see in infrared light, the night sky would look as bright as daylight! So when we’re trying to detect the faint heat signatures of distant astronomical objects, a glowing, warm atmosphere is almost impossible to see through. This is why we must cool the WISE telescope to a mere 12 degrees above absolute zero (minus 438 Fahrenheit). Being in space with a cold telescope makes such a huge difference that the relatively modest-size WISE telescope, which is 40 centimeters (16 inches) in diameter, is equivalent in sensitivity to literally thousands of 8-meter (26-foot) telescopes on the ground. That small WISE telescope packs a punch.

So with that cleared up, we’re just about ready to put WISE into the nose cone and crane it up onto the Delta II rocket that’s waiting for us on the launch pad. Let’s go see some stars!

Rocks and Stars with Amy: Sizing Up Near-Earth Asteroids

Wednesday, November 12th, 2008

By Amy Mainzer

Rocks and Stars with Amy

Asteroids. The word conjures images of pitted rocks zooming through space, the cratered surfaces of planets and moons, and for some, memories of a primitive video game. Just how hazardous are these nearest neighbors of ours? We think that one contributed to the extinction of the dinosaurs, giving rise to the age of mammals. How likely is this to happen again?

The Wide-field Infrared Explorer (WISE) mission, an infrared telescope launching in about a year, will observe hundreds of near-Earth asteroids, offering unique insights into this question. The risk posed by hazardous asteroids is critically dependent on how many there are of different sizes. We know that there are more small asteroids than large ones, but how many more, and what are they made of?

asteroidAsteroids reflect sunlight (about half of which is the visible light that humans see), but the sun also warms them up, making them glow brightly in infrared light. The problem with observing asteroids in visible light alone is that it is difficult to distinguish between asteroids that are small and highly reflective, or large and dark. Both types of objects, when seen as distant points of light, can appear equally bright in visible light. However, by using infrared light to observe asteroids, we obtain a much more accurate measurement of their size. This is because the infrared light given off by most asteroids doesn’t depend strongly on reflectivity.

WISE will give us a much more accurate understanding of how many near-Earth asteroids there are of different sizes, allowing astronomers to better assess the hazard posed by asteroids. The danger posed by a near-Earth asteroid depends not only on its size, but also on its composition. An asteroid made of dense metals is more dangerous than one of the same size made mostly of less dense silicates. By combining infrared and visible measurements, we can determine how reflective the asteroids are, which gives us some indication of their composition.

Rocks and Stars with Amy: An Infrared Glimpse of What’s to Come

Tuesday, July 22nd, 2008

By Amy Mainzer

Rocks and Stars with Amy

Almost everyone has had the frustrating experience of getting lost. To avoid this problem, the savvy traveler carries a map. Similarly, astronomers need maps of the sky to know where to look, allowing us to make the best use of precious time on large telescopes. A map of the entire sky also helps scientists find the most rare and unusual types of objects, such as the nearest star to our sun and the most luminous galaxies in the universe. Our team (lead by our principal investigator, Dr. Ned Wright of UCLA) is building a new space telescope called the Wide-field Infrared Survey Explorer that will make a map of the entire sky at four infrared wavelengths. Infrared is a type of electromagnetic radiation with a wavelength about ten or more times longer than that of visible light; humans perceive it as heat.

Why do we want to map the sky in the infrared? Three reasons: First, since infrared is heat, we can use it to search for the faint heat generated by some of the coldest objects in the universe, such as dusty planetary debris discs around other stars, asteroids and ultra-cold brown dwarfs, which straddle the boundary between planets and stars. Second, we can use it to look for very distant (and therefore very old) objects, such as galaxies that formed only a billion years after the Big Bang. Since light is redshifted by the expansion of the universe, the most distant quasars and galaxies will have their visible light shifted into infrared wavelengths. And finally, infrared light has the remarkable property of passing through dust. Just as firefighters use infrared goggles to find people through the smoke in burning buildings, astronomers can use infrared to peer through dense, dusty clouds to see things like newborn stars, or the dust-enshrouded cores of galaxies.