Ok, legitimate post! Yay break!
Today I present the only part of astronomy that I've followed religiously through my humanities phase: space weather!
What is space weather? It's the interactions between the Sun (and what it throws off) and the Earth (or other planets, but we're egocentric). Aurorae are the most famous visual manifestation of space weather, but there's a lot more to it. To understand the phenomena, we should start with a basic understanding of the composition of the Sun and our little home rock...
The Sun: this site (click here) gives a good, if slightly technical, description of the Sun's layers. As an overview, the Sun is essentially one vast ball of hydrogen gas (~91% H atoms), which is so immensely large that the hydrogen in the core gets crushed under its own "weight" into helium via nuclear fusion.* However, it's also got layers, like the Earth does. There's a large convective layer that mixes the extremely hot gas around the Sun's interior, and this creates electromagnetic currents. These currents run like strands through certain localities; they are not consistent throughout the Sun -- remember this, it's is important later. The outermost layer spins like a skin on a spherical pudding (insert typical physicist joke on spherical objects here). Much like the Earth's crust, it spins at a different speed from the lower layers; however, unlike the Earth's crust, the section near the equator spins once every 25 days, while the poles rotate once every 36 days. This causes something like friction at the regions where the speeds differ.
I'll carry on with the Earth next time; that's right, I'm leaving you with a cliff-hanger! 'Til next time, redshifted readers! And merry Christmas!
*N.B.: I put weight in quotes here, because weight and mass aren't the same thing. To use the age-old example, you weigh about 1/6 of your normal Earth weight on the Moon, but you certainly haven't shrunk -- in other words, your weight has changed but your mass hasn't. This is a function of the mass of the object you're standing on (or in, in the case of the hydrogen atoms in the Sun). In space, this becomes important, since gravity has a different magnitude for every star, planet, etc.
Monday, December 24, 2012
Wednesday, December 19, 2012
Frustration with the Red Planet
Finals are, in fact, over, so I can re-prioritize this. The first thing I did in catching up on the astronomy news I missed in the last week or two was checking up on the Mars rover.
I didn't want to sound like a spoiled child. But come on, there's been no real data released since that measly little announcement at the conference at the beginning of December! Curiosity's been "investigating" rocks, taking photos, sniffing the air, and digging around for over five months. It would be really nice to have heard more than "we didn't expect the wind to blow in this direction" and "oh look, more chlorates."
Short post tonight, just venting the frustration. I know they have to sift their own data for some time, but after this long I would've expected we'd at least have whatever new info they've gleaned from the first on-the-ground photos.
I didn't want to sound like a spoiled child. But come on, there's been no real data released since that measly little announcement at the conference at the beginning of December! Curiosity's been "investigating" rocks, taking photos, sniffing the air, and digging around for over five months. It would be really nice to have heard more than "we didn't expect the wind to blow in this direction" and "oh look, more chlorates."
Short post tonight, just venting the frustration. I know they have to sift their own data for some time, but after this long I would've expected we'd at least have whatever new info they've gleaned from the first on-the-ground photos.
Monday, December 10, 2012
Kids in Astronomy
I was invited by a friend recently to hold an astronomy night for some kids. Now, I've never been known as a creative person, so where education types and elder sisters would be going nuts with tubes of glitter and marshmallows, I draw a blank. I know the things that make me excited about space, but the idea of that row of prematurely-jaded faces gives me the heebie-jeebies. I didn't understand those kids when I was their age; I understand them even less now.
So, I think about how I was when I was a pre-teen. The thing I wanted most was to have my intellect be considered the equal of any adult's. Just because I was in a pint-sized body, I reasoned, didn't mean that I couldn't grasp the concepts of quantum entanglement or multiple dimensions. One memory is particularly distinct. I was sitting on my bed, surrounded by my intro-level astronomy books. They were basically glorified picture-books, all bright colours and little text. I had a sheet of paper, with childish scrawling trying to piece together bits on black holes from each book. I was so frustrated. How could these authors introduce topics like singularities, and then just move on without explaining how they work, what we've seen, what we've calculated? It would be like killing Scheherazade on the 50th night. What's the point?
The bottom line is simple: children aren't stupid, they are untaught. A plethora of studies have shown that in so many topics, kids command flexibility and insight of mind that adults spend the rest of their lives trying to recreate. If anyone should be being fed our most complicated problems, it should be them. They have curiosity, intelligence, and imagination, and are unfettered by preconceptions about the so-called "laws" of the Universe.
So what am I going to tell these kids? I'm going to think of the "big concepts" that are supposed to be too much for their minds, and explain as much information as I can about them. I'm going to respect their brains, treat them as capable thinkers instead of cutesy factoid ingesters. Then I'm going to let them talk about it, stew in it, come up with solutions I bet would widen the eyes of any physicist. If we want to rehabilitate our nation's science education, this is how we need to start.
So, I think about how I was when I was a pre-teen. The thing I wanted most was to have my intellect be considered the equal of any adult's. Just because I was in a pint-sized body, I reasoned, didn't mean that I couldn't grasp the concepts of quantum entanglement or multiple dimensions. One memory is particularly distinct. I was sitting on my bed, surrounded by my intro-level astronomy books. They were basically glorified picture-books, all bright colours and little text. I had a sheet of paper, with childish scrawling trying to piece together bits on black holes from each book. I was so frustrated. How could these authors introduce topics like singularities, and then just move on without explaining how they work, what we've seen, what we've calculated? It would be like killing Scheherazade on the 50th night. What's the point?
The bottom line is simple: children aren't stupid, they are untaught. A plethora of studies have shown that in so many topics, kids command flexibility and insight of mind that adults spend the rest of their lives trying to recreate. If anyone should be being fed our most complicated problems, it should be them. They have curiosity, intelligence, and imagination, and are unfettered by preconceptions about the so-called "laws" of the Universe.
So what am I going to tell these kids? I'm going to think of the "big concepts" that are supposed to be too much for their minds, and explain as much information as I can about them. I'm going to respect their brains, treat them as capable thinkers instead of cutesy factoid ingesters. Then I'm going to let them talk about it, stew in it, come up with solutions I bet would widen the eyes of any physicist. If we want to rehabilitate our nation's science education, this is how we need to start.
Monday, December 3, 2012
Brown Dwarves
I always feel like saying that is a slur, somehow...anyway, short post tonight (heading towards finals...who thought it was a good idea to hold regular exams a week before finals? Just cover the material in the final!) on brown dwarves.*
Brown dwarves are small objects that fill the rather broad size gap between planets and stars. Essentially failed stars, they start at around 12-15 Jupiter masses and go up to...well, the size of ignition, about 10% of the Sun's mass.
What's a failed star? It's an object that started collecting gas from a nebula (hydrogen, some helium maybe), and may even have created a disk of swirling material. Unfortunately, for whatever reason, it ran out of gas to accumulate. This means that its total mass was insufficient to crush the hydrogen atoms at its core into each other -- creating helium through nuclear fusion, and consequently kick-starting its life as a star. Instead, it just sits there like a largish ball of matter, quietly wiling away time.
Ok, that's why they're not stars, but what differentiates brown dwarves from rogue planets? Well, dwarves, ironically, are just too big. There are a few other differences, although if you look too closely, you'll find that astronomers are still a little fuzzy on the details.
Firstly, their pseudo-stellar-disk method of formation is similar to that of a star, not a typical planet. Many rogue planets are presumed to have been slingshot from an unstable orbit around a multi-star system. Not so with brown dwarves.
Secondly, they are hot gaseous bodies; most of our planets, and the other planets we've found outside our own solar system, are either terrestrial (can be hot or cold) or Jovian, which are typically cold. This is related to where they form: terrestrial bodies form closer to the star, with less chance of capturing or holding onto gases; gas giants form outside the "frost line," where most gases condense to liquids or ices.** Contrary to this, brown dwarves do not give off much light in the visible spectrum, if any, but they emit a good deal in the infrared (IR) spectrum. Compare the images from Jupiter in the IR spectrum here and an image of a brown dwarf binary system here.Other images are more dramatic, but clearly even from a far greater distance, the brown dwarves give off a great deal more infrared radiation.
Thirdly, planets differentiate if they're made out of more than one element (go look up diamond exoplanets, pretty awesome). Heavy metals like iron and nickel sink to the core, and lighter elements rise to the surface or atmosphere. Brown dwarves are just a ball of mush. Its gases may have been there since formation, or a small amount of hydrogen fusion may have occurred early in life; physicists are still arguing over the parameters.
So, brown dwarves. They're hard to detect and they make the border fuzzy between what seemed previously to be pretty nailed-down definitions. They aren't stars, and they aren't habitable. We can't quite seem to figure out what they're for, in the grand scheme of things. If I figure it out, I'll let you all know.
*Yes, dwarves; I hate American spelling.
**There are "hot Jupiters" being found by recent exoplanet searches, but the term is relative; they're still quite cold, and they are believed to have migrated inward towards their star from their original orbit outside the frost line.
Brown dwarves are small objects that fill the rather broad size gap between planets and stars. Essentially failed stars, they start at around 12-15 Jupiter masses and go up to...well, the size of ignition, about 10% of the Sun's mass.
What's a failed star? It's an object that started collecting gas from a nebula (hydrogen, some helium maybe), and may even have created a disk of swirling material. Unfortunately, for whatever reason, it ran out of gas to accumulate. This means that its total mass was insufficient to crush the hydrogen atoms at its core into each other -- creating helium through nuclear fusion, and consequently kick-starting its life as a star. Instead, it just sits there like a largish ball of matter, quietly wiling away time.
Ok, that's why they're not stars, but what differentiates brown dwarves from rogue planets? Well, dwarves, ironically, are just too big. There are a few other differences, although if you look too closely, you'll find that astronomers are still a little fuzzy on the details.
Firstly, their pseudo-stellar-disk method of formation is similar to that of a star, not a typical planet. Many rogue planets are presumed to have been slingshot from an unstable orbit around a multi-star system. Not so with brown dwarves.
Secondly, they are hot gaseous bodies; most of our planets, and the other planets we've found outside our own solar system, are either terrestrial (can be hot or cold) or Jovian, which are typically cold. This is related to where they form: terrestrial bodies form closer to the star, with less chance of capturing or holding onto gases; gas giants form outside the "frost line," where most gases condense to liquids or ices.** Contrary to this, brown dwarves do not give off much light in the visible spectrum, if any, but they emit a good deal in the infrared (IR) spectrum. Compare the images from Jupiter in the IR spectrum here and an image of a brown dwarf binary system here.Other images are more dramatic, but clearly even from a far greater distance, the brown dwarves give off a great deal more infrared radiation.
Thirdly, planets differentiate if they're made out of more than one element (go look up diamond exoplanets, pretty awesome). Heavy metals like iron and nickel sink to the core, and lighter elements rise to the surface or atmosphere. Brown dwarves are just a ball of mush. Its gases may have been there since formation, or a small amount of hydrogen fusion may have occurred early in life; physicists are still arguing over the parameters.
So, brown dwarves. They're hard to detect and they make the border fuzzy between what seemed previously to be pretty nailed-down definitions. They aren't stars, and they aren't habitable. We can't quite seem to figure out what they're for, in the grand scheme of things. If I figure it out, I'll let you all know.
*Yes, dwarves; I hate American spelling.
**There are "hot Jupiters" being found by recent exoplanet searches, but the term is relative; they're still quite cold, and they are believed to have migrated inward towards their star from their original orbit outside the frost line.
Wednesday, November 28, 2012
Can You See Me Now?
I've mentioned this before, but one of the things that I find the most amazing about space is the vastness. To quote the Hitchhiker's Guide to the Galaxy (I often do), "Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly
big it is." It's very true. The more you think about the distances and time frames involved in properly studying the Universe, the more immense and incalculable it seems.
This bothers a lot of people, in much the same way as looking down from a height does. I'm going to take advantage of this opportunity to evoke the sensation in you, readers. Thinking that it takes 25,000 miles to go once around our planet's equator seems like a fairly large distance, right? It's a little over twice as far as the average person commutes to work in a year (my own calculations, based on Census data -- see bottom of page for how I got it). Then you think that you'd have to drive 9.5 times the Earth's circumference to get to our nearest neighbor, the Moon. To drive to Mars at the same speed, you would have to cover 3000 times the distance of your annual commute, or 1440 Earth circumferences. All that, and we haven't even left the inner solar system yet, much less looked at other stars.
It just gets more staggering from there; beyond our solar system are widely-spaced stars, beyond our local stars are the far-flung arms of our galaxy, beyond our galaxy are distant other galaxies in the Local Group, beyond the Local Group are other chains of galaxies spreading out into the Universe, at distances where even the light of billions of suns are a faint smudge in our telescopes. Just outside the (suddenly tiny) confines of our atmosphere is a vast, black stretch of...almost nothing...for distances that still take our most modern propulsion systems months to travel to.
And that's just space; don't look at time scales unless you want to feel real cosmic vertigo.
I find this all oddly comforting. There's something intensely personal about the fact that, in all this vastness, there is one tiny rock around one totally average star that is just right for our form of life to develop. Then there's all the other rocks out there that could support the same type of life. And all the ones that could have other kinds of life that we wouldn't even recognize. It doesn't matter how you think this Universe started, scientific or otherwise -- anyone who can think about these things and not get totally awestruck is missing out on one of the biggest beauties we know.
So I want to share some of the things that help make the Universe a warmer, fuzzier place to think about again:
*Fun Census calculations: I used the 2011 ACS numbers for average commute time for the entire US. (while I have your ear, the American Community Survey recently had its funding axed in Congress; this seriously erodes the information we have about the state of our nation's populace. Go read about about the fight, it was all over major media sources.) This number was 25.3 minutes. I assumed 55 mph as a median driving speed, to factor in both highways and local traffic. This gives 23 miles commute, one-way. Double that for a day's trip, 46 miles. Now, multiply that by the traditional 5 day workweek and 50 weeks of work per year, and you get approximately 11,600 miles per year.
This bothers a lot of people, in much the same way as looking down from a height does. I'm going to take advantage of this opportunity to evoke the sensation in you, readers. Thinking that it takes 25,000 miles to go once around our planet's equator seems like a fairly large distance, right? It's a little over twice as far as the average person commutes to work in a year (my own calculations, based on Census data -- see bottom of page for how I got it). Then you think that you'd have to drive 9.5 times the Earth's circumference to get to our nearest neighbor, the Moon. To drive to Mars at the same speed, you would have to cover 3000 times the distance of your annual commute, or 1440 Earth circumferences. All that, and we haven't even left the inner solar system yet, much less looked at other stars.
It just gets more staggering from there; beyond our solar system are widely-spaced stars, beyond our local stars are the far-flung arms of our galaxy, beyond our galaxy are distant other galaxies in the Local Group, beyond the Local Group are other chains of galaxies spreading out into the Universe, at distances where even the light of billions of suns are a faint smudge in our telescopes. Just outside the (suddenly tiny) confines of our atmosphere is a vast, black stretch of...almost nothing...for distances that still take our most modern propulsion systems months to travel to.
And that's just space; don't look at time scales unless you want to feel real cosmic vertigo.
I find this all oddly comforting. There's something intensely personal about the fact that, in all this vastness, there is one tiny rock around one totally average star that is just right for our form of life to develop. Then there's all the other rocks out there that could support the same type of life. And all the ones that could have other kinds of life that we wouldn't even recognize. It doesn't matter how you think this Universe started, scientific or otherwise -- anyone who can think about these things and not get totally awestruck is missing out on one of the biggest beauties we know.
So I want to share some of the things that help make the Universe a warmer, fuzzier place to think about again:
- SETI (http://www.seti.org/): de-funded by the government after less than a year's actual operation, the Search for ExtraTerrestrial Intelligence has not been idle. Looking for signals from other planets, the now-private group uses its own radio telescopes (or gets time on other telescopes pointing in likely directions) and gathers data. The head scientist, Seth Shostak, recently claimed that SETI was likely to find an alien signal within the next 25 years . You can even help them sort through it by running a SETI@home program while your computer is idling.
- The Drake Equation: this equation applies to our galaxy, or any other galaxy with at least one civilization. It basically summarizes all of intelligent-life astrobiology. Made up of about 7 terms (depending upon which version you use), it tells you just how likely it is to find intelligent life advanced enough to be broadcasting signals into space in your galactic vicinity at the present time. The trick is that we don't have exact numbers for most of the terms, but the upshot is that all but the most conservative estimates turn up at least a few alien civilizations in our galaxy. A good introduction to the nitty-gritty of the equation can be found here (http://www.pbs.org/wgbh/nova/space/drake-equation.html).
- Hubble Image Gallery (http://hubblesite.org/gallery/): This might seem counter-intuitive, but there's just something about seeing these beautiful, colorful pictures that makes the Universe look like a friendlier place.
- Things Close to Home (http://www.nasa.gov/mission_pages/cassini/main/index.html and http://mars.jpl.nasa.gov/msl/): if you're feeling a little...a-claustrophobic still, take a gander at some of the neighborhood scenery. NASA's Cassini-Huygens and Curiosity missions are returning routinely gorgeous pictures of planets that are within our reach, our cosmic siblings. Cassini is focusing on Saturn and its moons (some of which are prime local candidates for life), and Curiosity is, of course, on Mars. Check out especially the skyline pictures from Curiosity, and think about how those things that look like low hills are mountains up to 5 miles high!
*Fun Census calculations: I used the 2011 ACS numbers for average commute time for the entire US. (while I have your ear, the American Community Survey recently had its funding axed in Congress; this seriously erodes the information we have about the state of our nation's populace. Go read about about the fight, it was all over major media sources.) This number was 25.3 minutes. I assumed 55 mph as a median driving speed, to factor in both highways and local traffic. This gives 23 miles commute, one-way. Double that for a day's trip, 46 miles. Now, multiply that by the traditional 5 day workweek and 50 weeks of work per year, and you get approximately 11,600 miles per year.
Tuesday, November 27, 2012
The Economic Morality of Space Exploration
Also known as, how I justify spending billions of dollars on space programs. This is a topic I've debated in my own head for a while. I'm a minimalist when it comes to governmental theory, so I've struggled with the idea of a national space agency and the huge amounts of money that get poured into it. In the end, I've come out pro-NASA (and it's not just because I want a job eventually).
The pros and cons of most government agencies get rehashed every election year, and when the economy is going down the drain this badly, a lot of people start looking to slash anything that doesn't benefit everybody in an obvious way. Here's my thinking:
The pros and cons of most government agencies get rehashed every election year, and when the economy is going down the drain this badly, a lot of people start looking to slash anything that doesn't benefit everybody in an obvious way. Here's my thinking:
- Saving our behinds in the future. Honestly, no one knows right now what's happening with our planet, on multiple levels. Not to sound alarmist, but our climate is changing measurably within a single generation, the ice caps are melting, storms are getting larger and more violent, and our magnetic envelope is slowly but surely disintegrating. None of this is new in our planet's history, and if archeological evidence is correct, we're overdue for a lot of what's coming. But most of these changes have each been associated with the near- or utter extinction of the predominant species on the planet at the time, and we have no solid idea of the time scales upon which these events took place in the past. This is not very comforting for us (or dolphins, or mice, if you believe Douglas Adams).
How does this justify our space program? Well, first there's the worst-case scenario, in which we have to evacuate the planet before it becomes the next Venus or Mars (depending on your preferred doomsday disaster). Space exploration teaches us the tricky bits of living elsewhere, so our homeworld exit isn't a strictly sink or swim situation. We could also learn how to nudge other worlds' climates into being habitable -- a la terraforming -- to make the adjustment easier for the non-astronaut population. - Learning how to save/preserve our own planet. Take a look around at how many things we use on Earth are from NASA. Seriously. Car seats, your cell phone camera, that crinkly foil-y blanket you keep in your trunk, even your Brita filter in your fridge all came from things developed by our national space labs (here and here are overviews of some more items). With a track record like that, the idea that they wouldn't learn and share strategies to help our planet by researching and exploring others is a little far-fetched. Terraforming Mars may take tens of thousands of years, but if we learn how to do it, we may be able to keep Earth from needing to be terraformed itself.
- Soft power. Look, we're America. Designing and manufacturing things that go into space makes us look really good; we don't need a Cold War to justify shining up our soft power quotient. And it gives our people the opportunity to be part of something scientific in our country, which is an area that we are falling further and further behind in compared to developing nations. We need to strengthen our science base in both the public and private sectors, and show the world that we do more than just make movies featuring warp drives...we can build them (which will probably be my next blog post, since it's exciting me so much).
to
Wednesday, November 21, 2012
Mars News...Sort of
Might as well strike while the iron's hot with this story...if you can call it that yet. I posted it on my Twitter (click here) the other day, but no one reads that.
Everyone is excited because the lovely science-y types over at MSL announced -- well, that something very interesting is about to pop, but that they're checking their data a few more times before they'll announce it (click here). Apparently the SAM instrument (click here -- sorry, if I just code the link in-text, it's not visible) has turned up a discovery of some sort.
Now I'm going to pretend for a few minutes that I'm qualified to speculate on this, because I've been following this mission like nerds follow Joss Whedon. Also, I've actually done coursework on astrobiology, so I know a teensy bit more than the average news reader.
Background info first: the rover has been collecting soil samples on Mars. They scooped and then dumped out the first few, because they want to make absolutely sure that the samples aren't contaminated by anything Earth-originating. It would be pretty embarrassing to claim to find life and later realize that someone sneezed on the shovel (just kidding, they do insane amounts of decon work before it gets launched; there's bona fide international laws about contaminating other planets -- click here). Anyway, the first sample was actually deposited in the spectroscopy machine, and now they're saying they have a discovery.
Overview of Spectroscopy: it's...just really, really cool. Basically, you beam white light into an object and pass the light that comes out the other side through a kind of prism, separating it into its constituent colors. If you're doing emission spectroscopy, what you get looks like a multicolor bar code. If you're doing absorption spectroscopy, you get the opposite -- a rainbow bar with red light at one end and purple at the other, and black vertical lines in certain areas. In both cases, the lines are the fingerprints of elements. Different atoms absorb light of certain wavelengths, always. So those wavelengths, seen together, always point to that particular element. Depending upon the patterns of the lines (and in more sophisticated readings, how much light is absorbed at each wavelength), you can tell what chemicals compose the object you're looking at, without taking it apart, using nothing but light. It's incredible.
So, what do I think they've found? I bet they've found some sort of complex organic molecule, maybe an amino acid or two. The simpler molecules that life are based on (hydrocarbons and other organics) can be found in a surprising range of places in the Universe, from asteroids to nebulae. It seems like the more we look, the more we see that carbons and hydrogens just can't wait to bond into the things our cells are made of, with a little help from cosmic radiation and/or water. However, amino acids and proteins are much harder to form, and don't seem to happen without a lot more prodding (lots of electrical current, or RNA/DNA instructions -- which are proteins themselves, you can see the problem).
It's unlikely that they've found current life, with the amount of radiation that hits the topsoil there, and the lack of water. It's also unlikely that they found dead signs of life, since that would be hard to find on the surface after billions of years, and microfossils are annoying hard to confirm as such. I also think it's improbable, as some naysayers are predicting, that they're going to announce definitively that there is no life. That would be ridiculous to do from a single soil sample.
It would be nice for them to have found something that would make a great headline -- MARS LIFE FINALLY CONFIRMED. But my guess is that they found something that only other scientists and astrobiology nuts are going to be excited about, while science-column journalists for newspapers scratch their heads about how to phrase the real discovery. PREPARE FOR...Prerequisites for Life Tentatively Confirmed on Martian Surface. Shiny.
Everyone is excited because the lovely science-y types over at MSL announced -- well, that something very interesting is about to pop, but that they're checking their data a few more times before they'll announce it (click here). Apparently the SAM instrument (click here -- sorry, if I just code the link in-text, it's not visible) has turned up a discovery of some sort.
Now I'm going to pretend for a few minutes that I'm qualified to speculate on this, because I've been following this mission like nerds follow Joss Whedon. Also, I've actually done coursework on astrobiology, so I know a teensy bit more than the average news reader.
Background info first: the rover has been collecting soil samples on Mars. They scooped and then dumped out the first few, because they want to make absolutely sure that the samples aren't contaminated by anything Earth-originating. It would be pretty embarrassing to claim to find life and later realize that someone sneezed on the shovel (just kidding, they do insane amounts of decon work before it gets launched; there's bona fide international laws about contaminating other planets -- click here). Anyway, the first sample was actually deposited in the spectroscopy machine, and now they're saying they have a discovery.
Overview of Spectroscopy: it's...just really, really cool. Basically, you beam white light into an object and pass the light that comes out the other side through a kind of prism, separating it into its constituent colors. If you're doing emission spectroscopy, what you get looks like a multicolor bar code. If you're doing absorption spectroscopy, you get the opposite -- a rainbow bar with red light at one end and purple at the other, and black vertical lines in certain areas. In both cases, the lines are the fingerprints of elements. Different atoms absorb light of certain wavelengths, always. So those wavelengths, seen together, always point to that particular element. Depending upon the patterns of the lines (and in more sophisticated readings, how much light is absorbed at each wavelength), you can tell what chemicals compose the object you're looking at, without taking it apart, using nothing but light. It's incredible.
So, what do I think they've found? I bet they've found some sort of complex organic molecule, maybe an amino acid or two. The simpler molecules that life are based on (hydrocarbons and other organics) can be found in a surprising range of places in the Universe, from asteroids to nebulae. It seems like the more we look, the more we see that carbons and hydrogens just can't wait to bond into the things our cells are made of, with a little help from cosmic radiation and/or water. However, amino acids and proteins are much harder to form, and don't seem to happen without a lot more prodding (lots of electrical current, or RNA/DNA instructions -- which are proteins themselves, you can see the problem).
It's unlikely that they've found current life, with the amount of radiation that hits the topsoil there, and the lack of water. It's also unlikely that they found dead signs of life, since that would be hard to find on the surface after billions of years, and microfossils are annoying hard to confirm as such. I also think it's improbable, as some naysayers are predicting, that they're going to announce definitively that there is no life. That would be ridiculous to do from a single soil sample.
It would be nice for them to have found something that would make a great headline -- MARS LIFE FINALLY CONFIRMED. But my guess is that they found something that only other scientists and astrobiology nuts are going to be excited about, while science-column journalists for newspapers scratch their heads about how to phrase the real discovery. PREPARE FOR...Prerequisites for Life Tentatively Confirmed on Martian Surface. Shiny.
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