## Archive for the ‘Earth’ category

### Big Sky Country

July 31, 2010

Well folks, I’m headed off to Big Sky Country tomorrow (aka Montana)! I’ll start the week at the MSL camera team meeting, where I will get all sorts of cool news about the MastCam, MAHLI and MARDI cameras which I will not be able to share with you.* After that, the lot of us will pack up and head to Glacier National Park to learn about the geology of the Belt-Purcell supergroup, and more generally, how to apply terrestrial geology to martian geology. I always enjoy field trips like this because I get to hike around on the rocks with a bunch of experts as well as many with less field experience, so there are lots of educational discussions. Also, did I mention the part where I get to drive and  hike around in spectacular scenery? Yeah. Times like this I’m reminded that my job Does Not Suck.

I’ll try to write a post or two about the trip once I actually understand the geology we’re going to see a little more. Hopefully the weather will cooperate and I’ll have some pretty pictures to share too!

*One of the difficulties with actually being involved in missions is that I can’t just write about all the cool stuff I hear about. I got scolded when this blog was just starting out for posting information before JPL or NASA had approved of it, so I tend to err on the side of caution now. It’s frustrating, but there’s nothing I can really do.

### New Deep Sea Vents Discovered in the Caribbean

July 22, 2010

The hybrid robotic vehicle Nereus is recovered after searching for new hydrothermal vents along the Mid-Cayman Rise. Image credit: Woods Hole Oceanographic Institution

Here’s the second of my recent Universe Today Articles: scientists have discovered new deep sea vents in the Caribbean that will teach us more about sunless ecosystems. Good to know if we ever want to look for life in the oceans of Europa some day! Check out the article here.

### Solar System Tour: Earth

June 6, 2010

This is Earth, the third planet from the sun. I’m hoping, of all the planets, you’re most familiar with this one. Hopefully, though, you’re about to learn a little more about home. When seen from space, one of the most striking features of the Earth is all the water. Our planet’s surface is about 70% water. Earth is the only planet known with liquid water currently on the surface. Mars once had liquid water, and water ice is all over the place, but Earth’s water oceans are unique. The average temperature on earth is about 59 degrees F (15 C). Normally, at earth’s distance from the sun, it would be a lot colder, but we have an atmosphere to help us out. Just like Venus’ atmosphere traps heat and keeps the surface blazing hot, our atmosphere keeps the planet nice and warm. You might wonder what the big fuss about the greenhouse effect is, if it keeps us warm. The big fuss is, that if too much greenhouse gas goes into the atmosphere and traps too much heat, the planet will get too warm and many types of life will start to die. Even a few degrees increase can have major effects.

The earth has a core of solid iron and other heavy materials, surrounded by a liquid iron outer core. The core rotates inside the planet and creates a strong magnetic field. Outside the core is the mantle, a thick layer of hot (but not molten!) rock. Above the mantle is the crust, a thin layer of rocks.

The earth’s crust is broken into “tectonic plates” which move around. When plates collide, they crumple up and form mountains, like the Himalayas. When the plates spread apart, magma oozes up from the mantle and hardens into new rocks. Earthquakes are caused when the edges of plates grind together, and volcanos are often found where two plates meet.

Because the plates are constantly moving around, melting, and reforming, earth’s surface is said to be “geologically active”. That’s why the earth doesn’t have very many craters compared to the moon and most other objects in the solar system. Earth does have some craters though. One of the most famous is the Barringer meteor crater in Arizona. This crater is almost a mile across and was made by a nickel-iron meteor about 150 feet across. The impact released the same amount of energy as exploding 20,000,000 tons of dynamite!

From the surface, the earth seems like a pretty big place, but in reality, it’s a tiny speck. Here is a picture of the earth that was taken by the Voyager 1 probe in 1990 from a distance of 3.7 billion (3,700,000,000) miles. The earth is the tiny dot. The streaks across the image are scattered light from pointing the camera so close to the sun. Click the picture to read a quote about it.

### How to cure the Avatar Blues

January 12, 2010

I was innocently browsing through my twitter list yesterday when I came across this article on CNN. The gist of it is that many people are experiencing depression after watching Avatar because the fictional world depicted is so beautiful and amazing that life back here on earth seems drab and boring.

Many people have responded to this story with shock and derision, and this definitely hints at some pre-existing issues for the folks who are feeling suicidal after watching a sci-fi film, but it also concerns me for another reason. It suggests a troubling lack of knowledge about the real world.

One person quoted in the article said: “When I woke up this morning after watching Avatar for the first time yesterday, the world seemed … gray. It was like my whole life, everything I’ve done and worked for, lost its meaning. It just seems so … meaningless. I still don’t really see any reason to keep … doing things at all. I live in a dying world.”

This really bothers me, because despite all the nasty things that humans have done to the world, it is a far cry from a dying world! (And if our world really is “dying” then shouldn’t we be out there trying to save it rather than despairing?) I can tell you this: studying other planets makes you realize that Earth is a paradise. And believe it or not, many of the “creative” flora and fauna in Avatar are based directly on living things here on Earth, past or present.

Remember those glowing spiral “plants” that Jake taps, causing them to curl up into their stem in the blink of an eye? They’re real! They exist in miniature in coral reefs around the world as “christmas tree worms”.

Jake Sully walks in awe through a glade of giant christmas tree worms.

Actual christmas tree worms in Bonaire.

What about those glowing mushrooms that he plays like drums? Yeah we’ve got those. Again, much smaller, but similar.

Glowing mushrooms really exist too!

And of course the seeds of the Tree of Life are obviously based on real-world jellyfish. James Cameron is a guy who knows all about the weird living things on our planet. Heck, have you seen his documentary “Aliens of the Deep”? It’s pretty obvious where he got some of his inspiration for the creatures in Avatar!

A deep-sea jellyfish from Cameron's "Aliens of the Deep".

Ok, but what about the sweet dragon-like creatures that they ride? I think people would notice if we had those flying around, taking out our helicopters and planes! Well no, they don’t exist now, but go back to the mesozoic and there are plenty of flying creatures, including this one which was taller than a giraffe when on the ground:

And how about good old Quetzalcoatlus, with a 30 foot wingspan?

Quetzalcoatlus had a wingspan comparable to some airplanes. The silhouette should look familiar to anyone who has seen Avatar...

So that’s the biology, but what about the moon itself? What about the floating mountains? The spectacular rock formations? Well, habitable moons probably do exist, and there are astronomers searching for them right now. Floating mountains would be rather difficult, but superconductors do, in fact, allow things to levitate. Take a look at Joe Shoer’s post about Avatar’s floating mountains if you don’t believe me. And the rock formations? Well, Earth doesn’t have arches of rock following magnetic field lines like iron filings, but we do have some pretty spectacular stuff, like caves full of giant crystals:

Spectacular crystal formations? Yeah, we've got that.

My point is this: yeah, it’s a shame that Pandora isn’t real. I was sad too when the movie ended and the credits rolled. But the world we live in is just as amazing. You won’t get rid of the Pandora blues just by watching Avatar endlessly, or running out and getting the Avatar video game. But much of what was in the movie was based on real things here on Earth. Many of the photos I’ve shown here are relatively recent discoveries. There is plenty of wonder to go around and plenty more to discover. And if you get tired of Earth, there are other planets in our solar system. Tired of those? Check out exoplanets. Still not enough? Head into the realm of astrophysics and you’ll never get bored. And for those longing to live like the Na’vi there are options too. Anthropologists regularly study native cultures and learn their ways. Or you could become an archaeologist and learn about past cultures by studying their artifacts.

Still not enough? Well, then instead of living in someone else’s fictional world, why not make your own? Become a science fiction or fantasy writer and see if you can do better than James Cameron. Who knows, maybe someday people will see your world and long to go there too.

Avatar’s vivid world should not be a source of depression, it should be a motivation to seek out (or create) the beautiful and the interesting and the fragile in our own world, to study and learn from it, and to preserve it so future generations can experience the wonder as well.

### Rings around the Earth – Implications

November 30, 2009

Last week I posted a video that speculates what it would look like if the Earth had rings like Saturn. Well, over at Quantum Rocketry, Joe Shoer has two excellent follow-up posts. First he calculated what the rings would really look like with gaps caused by Earth’s moons rather than just copying and pasting Saturn’s rings. Here’s a simulated image, but you should check out the full post for more info.

And then, even more thought-provoking, he went on to consider the implications that rings would have to civilization and early astronomy. His post is well worth a read. Here’s a teaser:

I’ll say that again: If the Earth had rings, the ancient Greeks, Chinese, and Egyptians might have had a sense of the scale of the Cosmos. The Romans and Indians might have known what a parsec is.

November 23, 2009

There’s a great video making the rounds showing what it would look like if Earth had a ring system like Saturn’s, including some gorgeous views from the ground. Of course, rings probably wouldn’t be stable with our moon, or at least would look very different, but that doesn’t take away from the coolness of this video. Enjoy!

### If This is Socialist Propaganda, Please, Send More

September 9, 2009

Surely by now you have heard that president Obama attempted to brainwash our nation’s children with socialist propaganda yesterday. It is apalling, isn’t it? An outrage! But have you actually heard or read what he said? I’ll let his words speak for themselves:

I want to start with the responsibility you have to yourself. Every single one of you has something that you’re good at. Every single one of you has something to offer. And you have a responsibility to yourself to discover what that is. That’s the opportunity an education can provide.

Maybe you could be a great writer — maybe even good enough to write a book or articles in a newspaper — but you might not know it until you write that English paper — that English class paper that’s assigned to you. Maybe you could be an innovator or an inventor — maybe even good enough to come up with the next iPhone or the new medicine or vaccine — but you might not know it until you do your project for your science class. Maybe you could be a mayor or a senator or a Supreme Court justice — but you might not know that until you join student government or the debate team.

Oh, but it gets worse:

What you’re learning in school today will determine whether we as a nation can meet our greatest challenges in the future.You’ll need the knowledge and problem-solving skills you learn in science and math to cure diseases like cancer and AIDS, and to develop new energy technologies and protect our environment. You’ll need the insights and critical-thinking skills you gain in history and social studies to fight poverty and homelessness, crime and discrimination, and make our nation more fair and more free. You’ll need the creativity and ingenuity you develop in all your classes to build new companies that will create new jobs and boost our economy.

We need every single one of you to develop your talents and your skills and your intellect so you can help us old folks solve our most difficult problems. If you don’t do that — if you quit on school — you’re not just quitting on yourself, you’re quitting on your country.

Problem solving skills? Critical thinking? Responsibility? MY kids will learn no such things!

The truth is, being successful is hard. You won’t love every subject that you study. You won’t click with every teacher that you have. Not every homework assignment will seem completely relevant to your life right at this minute. And you won’t necessarily succeed at everything the first time you try.

That’s okay. Some of the most successful people in the world are the ones who’ve had the most failures. J.K. Rowling’s — who wrote Harry Potter — her first Harry Potter book was rejected 12 times before it was finally published. Michael Jordan was cut from his high school basketball team. He lost hundreds of games and missed thousands of shots during his career. But he once said, “I have failed over and over and over again in my life. And that’s why I succeed.”

No one’s born being good at all things. You become good at things through hard work. You’re not a varsity athlete the first time you play a new sport. You don’t hit every note the first time you sing a song. You’ve got to practice. The same principle applies to your schoolwork. You might have to do a math problem a few times before you get it right. You might have to read something a few times before you understand it. You definitely have to do a few drafts of a paper before it’s good enough to hand in.

Don’t be afraid to ask questions. Don’t be afraid to ask for help when you need it. I do that every day. Asking for help isn’t a sign of weakness, it’s a sign of strength because it shows you have the courage to admit when you don’t know something, and that then allows you to learn something new. So find an adult that you trust — a parent, a grandparent or teacher, a coach or a counselor — and ask them to help you stay on track to meet your goals.

The story of America isn’t about people who quit when things got tough. It’s about people who kept going, who tried harder, who loved their country too much to do anything less than their best.

It’s the story of students who sat where you sit 250 years ago, and went on to wage a revolution and they founded this nation. Young people. Students who sat where you sit 75 years ago who overcame a Depression and won a world war; who fought for civil rights and put a man on the moon. Students who sat where you sit 20 years ago who founded Google and Twitter and Facebook and changed the way we communicate with each other.

So today, I want to ask all of you, what’s your contribution going to be? What problems are you going to solve? What discoveries will you make? What will a President who comes here in 20 or 50 or 100 years say about what all of you did for this country?

Patience? Perseverance? Willingness to ask for help? Sounds like socialism to me!

Ok. Seriously. In case the title didn’t clue you in, I’m being somewhat sarcastic here. I think it’s great that the president is willing to address students and encourage them to get an education. I think it is absurd to call this socialist propaganda. Is it US propaganda? You betcha: it’s all about helping this country become better by helping its people become better. But this is pretty much the most benign form of propaganda I can think of. It has none of the flag-waving jingoism and self-congratulation that many people mistake for patriotism, just an honest message that education is important for the future and that it is hard work.

It’s a message that more people should take to heart. Don’t think for one second that Obama thought he was talking only to students in this speech. This is a message to everyone. Education and hard work are key for the future of the US and the future of the world. How do you think we landed people on the moon? Education and hard work. How is it that the Mars rovers were so well-designed that they are still operating after more than 5 years on the surface of Mars? Education and hard work. When we send humans back to the moon and on to Mars, it will take education and hard work.

These values are the core of what NASA does, and they are at the heart of every challenge, both technical and social, facing the world. If the problems were easy, they would be solved already. But they aren’t, and we need to learn more and work hard to solve them.

As far as I can tell, protesting against the message of this speech must mean that people oppose either education or hard work or both. I’m sure there are people out there who do oppose those things, but are they really so proud of that? Or perhaps protesters just don’t like the idea of the president speaking to students when they should be learning their lessons? What lesson, particularly so early in the school year, is more important than the message that education is important, that hard work pays off, and that it is ok to ask for help?

Of course, the real reason that people protest this speech is because they dislike the president. I admit, I’d probably be annoyed at first if I heard that George W. Bush was going to be addressing the nation’s students. But if he had given the speech that Obama just did, I would commend it too, because the message was not political. It’s just good advice. There’s really no rational way to argue against the message here. For some reason, people assume that if someone they dislike says something, then it must be socialist propaganda. Well, if this is socialist propaganda, please send more.

Phil Plait over at Bad Astronomy has written his own post about the absurdity of the protests over this little speech that I encourage you to check out. I also encourage you to check out this Fact Check article that discusses Obama’s speech, as well as the speeches to school children given by George H.W. Bush and Ronald Reagan.

Update: It looks like NASA administrator Charles Bolden agrees that education is crucial for the future of NASA. Check out his latest Op-Ed in the Orlando Sentinel.

### Fire near JPL

August 30, 2009

Apologies for the silence on the blog lately. I’ve been trying to get caught up with work since I got back from the north woods of Michigan last sunday. However, I thought I should take a minute and mention the forest fires in LA that are threatening JPL . People on the MER team have been sending occasional updates and photos over the last few days as the fires inch closer to the Lab.

Best wishes for those in the LA area affected by this fire. Stay safe! No homes are reported lost yet, and let’s hope no telescopes or NASA labs will be lost either!

Emily Lakdawalla also has a post full of info about the fires over at the Planetary Society blog.

LA fires seen from the roof of a JPL building. (Photo by Mike Seibert)

Fires with JPL in the foreground. (Photo by Joy Crisp)

A jet dumps fire-retardant on the fires with JPL in the foreground. (Photo by Justin Maki)

Close-up of the tanker jet. (Photo by Justin Maki)

### Solar System Creator

July 10, 2009

As I mentioned last month, on top of research and grad school duties, I’m in the process of planning out a sci-fi novel. It began with the month-long outlining challenge “Midsommer Madness” over at the Liberty Hall writing site, and I am continuing with it in my spare time.

I am trying to make my novel grounded in reality whenever possible. It is set in a known star system, 55 Cancri. The 55 Cancri system has 5 known planets, but I also took some artistic license and added moons and small planets that observations would likely have missed. Then, once I had planets and moons, I needed to figure out which ones would be habitable!

I happen to know a thing or two about planets, so I put together a handy spreadsheet to use to calculate things like surface temperature, surface gravity and orbital period given things like how bright the star is, how far away the planet is, etc. Once I had the spreadsheet made, I realized that there are likely other people out there who might find it useful.

So, whether you are a writer trying to come up with a plausible setting for your bestselling sci-fi epic, or a student learning about the solar system, or just plain curious about planets, please feel free to use and modify this spreadsheet. Right now it is set up for our solar system to give you an idea of what reasonable values are for the different variables, and to show that the results are generally pretty good despite the simplicity of the calculations. If you find this useful or have any questions, feel free to contact me by leaving a comment on this post.

I described how I calculated the surface temperature below. You don’t need to read the explanation to use the spreadsheet: it should just work if you enter numbers, but I encourage you to try to follow the derivation. Even if you don’t follow the algebra, I tried to explain everything in words to give some conceptual understanding of the ideas behind the math, and the ideas are what matter.

Note for Students: The spreadsheet is free for you to use, but be sure you cite this page as a source. Also show your work for all calculations! Copying values from the spreadsheet without showing your work probably won’t earn you any points, and may be considered plagiarism, which is grounds for failure and/or expulsion at most schools. And really, it’s not that hard to do the calculations, especially since the rest of this post is spent walking you through them! You might even learn something!

Ok, so how does it work? Well, the calculation of a planet’s surface temperature is based on the very simple idea that if its average temperature is not changing, then the amount of energy the planet absorbs must match the amount that it emits. Pretty much common sense! If the amount in and out were different, then the temperature would change until they balanced!

First, the absorption. The energy source is the star, which has a certain luminosity $L$ (given in watts). This says how much energy the star puts out in all directions per second. We want to know how much energy per square meter hits the planet, so we take the luminosity and spread it out evenly over the surface of a sphere with a radius $R$ equal to the distance from the planet to the star. The surface area of a sphere is $A=4\pi R^2$, so the amount of energy from the star hitting each square meter of the planet’s cross section is: $L/A=\dfrac{L}{4\pi R^2}$

The planet’s cross section is just the area of a circle with the planet’s radius: $\pi r^2$. Note that we’re using the area of a circle and not a sphere! That’s because the starlight doesn’t hit the whole planet, it just hits the part of the planet that is visible. Can you see all sides of a sphere at once? Neither can I, and neither can the star. What we see is the 2 dimensional cross section: a circle.

So now we have an equation for how much energy the planet absorbs per second: $Energy Absorbed Per Second= \dfrac{L \pi r^2}{4\pi R^2}$

But that is assuming that the planet absorbs every bit of light that hits it, which we know isn’t true: we see planets in the night sky by their reflected light! So we can add a correction called albedo. Albedo, $A$, is the fraction of starlight that the planet reflects back out into space, and $(1-A)$ is the fraction of starlight a planet absorbs. So with that correction, our equation becomes: $Energy Absorbed Per Second= \dfrac{(1-A) L \pi r^2}{4\pi R^2}$

Now we have to figure out an expression for the energy that the planet emits. Here we have to make an assumption to simplify things: we assume that the energy absorbed by the planet is immediately redistributed evenly over the whole planet. Obviously this isn’t right, it is much warmer on the day side than the night side, but this assumption makes our lifes much easier. We just have to remember that the value we get is going to be an average of day and night temperatures.

We also assume that the planet radiates away its energy like a blackbody. A blackbody is something that absorbs and emits all radiation perfectly. We’re not going to worry too much about this assumption. For our purposes, planets are close enough to being blackbodies that it doesn’t matter much. I know, I know, we just made an adjustment for albedo two paragraphs ago, implying that the planet is not a perfect blackbody! Just calm down. It works pretty well, and that’s all we need.

Anyway, if we assume the planet is a uniform temperature blackbody, then we can use the handy equation for blackbody emission: $Energy Emitted Per Square Meter Per Second = \sigma T^4$. Sigma is called the Stefan-Boltzmann constant, and is given by $\sigma = 5.67\times 10^{-8} W m^{-2} K^{-4}$ To get rid of that pesky “per square meter” part of the equation, we just multiply by the surface area of the thing doing the emitting: in this case, the planet. Here we do use the surface area of a sphere, remember our assumption that the energy absorbed gets spread out over the whole surface? This is why we did that. The result is:

$Energy Emitted Per Second = 4 \pi r^2 \sigma T^4$

Now that’s a fine equation if your planet emits every bit of energy that it receives straight back to space. But that’s not how it works for planets with atmospheres. There’s this effect where the atmosphere traps energy in the system for a longer time, resulting in a warmer planet…  you may have heard of it: the Greenhouse Effect! It would be nice if we could add that to our model! If we don’t, we’ll never get the surface temperature right for a planet like Venus, where the greenhouse effect dominates.

To actually do a proper simulation of the greenhouse effect is very difficult and complicated, so instead we are going to use a fudge factor. The bottom line is that the greenhouse effect $GE$ reduces the amount of energy radiated from the surface that escapes to space. So we can do something very similar to our albedo adjustment: $GE$ gives the amount of energy that the atmosphere absorbs, and $1-GE$ gives the amount of energy that actually escapes to space. For the Earth $GE \approx 0.4$ and for Venus $GE \approx 0.99$. Our modified equation is now:

$Energy Emitted Per Second = (1-GE) 4 \pi r^2 \sigma T^4$

Now, remember why we were doing all of this? We want to find the planet’s average surface temperature $T$. To get this, we have to set our two equations equal to each other and solve:

$Energy Emitted Per Second = Energy Absorbed Per Second$

$(1-GE) 4 \pi r^2 \sigma T^4 = \dfrac{(1-A) L \pi r^2}{4\pi R^2}$

Look! The planet’s radius appears on both sides of the equation! That means it cancels out, and that a planet’s radius has no effect on its surface temperature! Ok, don’t get too excited, we still need to solve for T.

$T^4 = \dfrac{L (1-A)}{16\sigma\pi R^{2}(1-GE)}$

$T = \left(\dfrac{L (1-A)}{16\sigma\pi R^{2}(1-GE)}\right)^{1/4}$

Voila! There is the expression for the equilibrium surface temperature of a planet, taking into account the planet’s reflectivity and the greenhouse effect. I hope this sheds a little light into how to think about the energy budget of a planet, and how my spreadsheet works. Again, if you have any questions, post them in the comments and I’ll answer them!

### The Pale Blue Dot

April 22, 2009

What better Earth day message is there than this?

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

The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds.

Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves.

The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.

It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we’ve ever known.

— Carl Sagan, Pale Blue Dot, 1994