Don’t look for an update to my blog or any new posts for the next two weeks. We’re off on vacation and I won’t be electronically connected. I hope to come back with new inspiration!
Month: July 2008
Science on the Moon
This will have to be short today, I’m on the run headed from Ames to JSC.
The Lunar Science conference at Ames exceeded beyond the organizers dreams; twice as many people came as they had planned for. Almost all were scientists and researchers from around the world with new scientific questions about the moon and proposals on how to gather more data.
In short, if anybody asks “what more can we learn from the moon?” The answer is “A WHOLE LOT”.
After the scientific conference concluded, another set of meetings with representatives from 9 nations started. Every one of these nations has serious plans to send robotic spacecraft to the moon in the next few years. At the conclusion of this meeting, all parties signed a letter of intention setting up something called the International Lunar Network. We all agreed to exchange scientific data, to work together on selection of scientific instruments that would complement each other’s work, and on communications protocols. This was like a mini UN session! Wow.
This is the second age of lunar exploration and we are witnessing the start of it. Great things are in the wings and exciting times lie ahead!
Monday – Time for another true story
The Space Shuttle is the only manned winged vehicle to fly hypersonically. I have seen it fly almost directly overhead at Mach 15 – extraordinarily impressive. No other flying machine comes close. But the price to fly at hypersonic speeds is the subsonic L/D, near landing approaches the aerodynamics of the common brick (L/D is the ratio of lift to drag, one of the most important properties of any flying machine). Which is to say, the shuttle comes down fast; its glideslope on final approach is 7 times steeper than a commercial airliner. Think dive bomber. And the pilot only gets one chance to get it right. No go-around capability.
The number one job of the Entry Flight Director is to make sure the Commander has the very best situation for landing. No, that’s not right; if we were to wait for the very best situation the flights would have to be a lot longer than they are. No, the number one job of the Entry Flight Director is to make sure the Commander has an adequate situation for final approach and landing. Defining the dividing line between an unacceptable situation and marginally adequate situation takes about 25 pages of Flight Rules. The worst part about this whole thing is it revolves around the weather. Or more precisely – and even worse – the weather forecast.
The law of conservation of energy means that all the energy that went into getting the shuttle from the launch pad to earth orbit must be removed to get the shuttle from earth orbit to wheelstop on the runway. 99.8 % of the energy is taken out by air friction – which is why it gets really hot during re-entry. Any glider pilot will tell you that making a good landing is all about energy management. Energy management on the shuttle is particularly complex. Stay with me now. This is rocket science.
After deorbit and throughout entry you always want to keep just a tad more energy than you need to get to the runway, but not too much or you will overshoot the runway and plop down in the middle of nowhere without a runway in sight – considered to be poor form.
The band between too much energy and not enough energy gets tighter and tighter as the shuttle approaches the runway. Like baby bear, you want don’t want to be too hot or too cold, but just right. The tail of the shuttle acts as a conventional rudder but also splits down the middle to make what is called a “speed brake” or in pilot speak: the “boards.” As the speed brake opens up, the shuttle will slow down faster and faster. The minimum (closed) is 15% — don’t ask why, it’s a long story. At settings of the “boards” about 60%, the handling qualities for the pilot degrade.
Periodically before the predicted landing time, balloons are launched near the runway and tracked up to 50,000 feet altitude or so. This gives a profile of wind speed and direction. This information is fed into a computer program which assumes the shuttle is flown perfectly and it computes all kinds of interesting results. Among the most important results are predicted speedbrake setting on final approach and the predicted touchdown location on the runway. The touchdown target is 2,500 feet past the painted threshold stripe on the runway.
The shuttle touches more than twice as fast as a commercial airliner, 205 knots for heavy weight returns and 195 knots for lighter weight returns when the payload bay is empty. Only slightly faster and the tires will come apart. Not very much slower and the tail will drag before the wheels touch down.
So there I was, the rookie Entry Flight Director, in charge on my very first shuttle entry. Watching the weather, sweating, over-caffinated, about to be sick to my stomach, but radiating calm confidence to my team. In other words, it was just like every other time I was in charge at the Flight Director console.
I had studied all the previous shuttle entries, knew all the procedures by heart, had all the rules memorized, and had watched several previous landings sitting right beside an experienced Entry Flight Director. The secret is, of course, that no two landings are alike, and I was about to learn that the hard way.
It was a windy day at Edwards AFB. All real test pilots like to fly early in the morning before the winds build up. Shuttle landing times are determined by orbital mechanics and this was going to be an afternoon landing. Stiff winds started blowing hours before landing and the forecast for surface wind speed was just below the limit. No other runway would do, only the big concrete runway that runs in a southwesterly direction, straight into the prevailing winds.
The onboard computed guidance which the Commander would be following would try to get the shuttle to a landing 2,500 feet down the runway at 195 knots; the speedbrake would be automatically adjusted accordingly. With the winds that were measured aloft, the computer model predicted that even with the speedbrake closed (15% — not dissipating any excess energy) would come up short on the minimum distance past the threshold allowed by the rules, 1000 ft. Now, at the very end game, a pilot can trade airspeed for lift and thus distance down the runway. The rule of thumb is 10 knots of airspeed difference results in around 1000 ft of distance along the runway. If you land 10 knots too fast, touchdown will be short by 1/5 mile. If the pilot stretches the landing by holding off until the airspeed reads 10 knots lower, the tires will hit the pavement about 1/5 mile farther down.
The crew is ready to return, all the other parameters are GO, just that pesky wind and short touchdown prediction. I checked with the weather man; conditions were predicted to be worse later in the day and unacceptable tomorrow.
Time to go to the coffee pot and think this over. It is a myth to believe that all the important decisions are made at the Flight Director console or maybe in some conference room down the hall. All the really important decisions in Mission Control are made by the coffee pot in the hall right outside. Lots of ex-Flight Directors and other management types seem to show up when the Flight Director on duty stops by for a cup. Lots of good advice can be had there. On this particular day, the place was deserted. Nobody to help. Well, back to the console, the clock is ticking.
The Flight Dynamics Officer points out that there is an exception in the rules; for a lightweight orbiter, landing at 10 knots slower – at 185 rather than 195 knots – with a predicted touchdown at 1000 or more feet past the threshold is considered adequate. By making that adjustment in the computer model, with the balloon measured winds, the prediction is touchdown at 1100 feet with 185 knots and CLOSED SPEEDBRAKE. No energy reserves other than that 1100 feet back to the start of the runway. Any EXPERIENCED Entry Flight Director would have seen warning flags all over this!
But, I was a rookie. All the flight rule criteria is met – GO FOR DEORBIT!
During the hour between the deorbit burn (no turning back now) and landing, the winds got stronger. They got stronger on the surface and the balloons showed the winds increasing aloft. There was nothing we could do about it but tell the Cmmander. He did not sound happy when he acknowledged the call. The Capcom stopped making eye contact with me.
The landing looked great on TV. You can’t tell on the video where the touchdown spot was. A good landing and the crew was healthy. I was feeling good about life. The tag line on all the news reports was that the shuttle landed safely. As far as the public knew it was all routine and there had been no danger. My stomach stopped doing flip flops.
A couple of hours later, I got THE PHONE CALL. The commander was NOT HAPPY. As I’ve told you before, it is never a good thing to have a commander who is NOT HAPPY. He thought he wasn’t going to make it to the runway. He really had to stretch to make it over the threshold. Just what did I think I had been doing to put him in that situation? I had a low moment.
The next day the official numbers came in. The rubber marks where the main gear tires kissed the runway were 1176 feet past the threshold. Yeah! That is OK! But wait, further down the form, the speed of touchdown was 176 knots. Oh no! Not 195 knots which is the standard target or even the 185 knots special exception, the shuttle touched down at 176 knots! The Commander really did have to stretch it out. The computer models did the math: if touchdown had been at the target speed of 195 knots, the wheels would have hit the ground 130 feet BEFORE THE RUNWAY THRESHOLD. Not good.
There are a lot of things in space flight that can kill you. Having a rookie Flight Director is one of them. If you ever get assigned to a space flight, check to see who is sitting in the big chair in mission control before you agree to go. If it’s their first flight, or maybe even their third, you may want to ask for a ticket on another flight.
Oh, and that wasn’t the worst thing that I ever did to a commander on landing. But that’s another story for another day.
Odds and Ends
Tomorrow I’ll try to share another old Flight Director war story. The last one set off quite the email chain at work as all the old SRAG guys felt like I was complaining about their work; not at all. Let me set the record straight; the folks that keep watch over the crew’s health and their possible radiation exposure are thoroughly professional and very dedicated. And they mainly scare the Flight Director to death when they appear in the Flight Control Room. The moral of my previous story is that there is a lot to know about how to fly safely in space and rookie Flight Directors are dangerous. Tomorrow I’ll try to post another example of that.
I had a little free time in Paris and tried to exercise the other hemisphere of my brain by going to the Musee d’Orsay, which is an art museum specializing in late 19th century to early (pre WWI) 20th century art. I have a liking for the impressionist school and my friend from Marshall, Dr. John Horack likes the pointellists so I thought this would be a good place to improve my art appreciation. The museum is housed in a converted 19th century train station and I must say that the building itself is as much a work of art as anything inside. I am fascinated by trains and railroads and looking at this wonderful structure was great.
The art is wonderful, Renoir, Cezanne, Van Gogh, Monet, and many many more. It seemed like the artists have a few favorite subjects that appear again and again, however. Among the popular subjects are scenes from the Bible, French peasant life, French countrysides, Paris street scenes, and the number one favorite subject of all the artists: . . . nekkid ladies. Hmm. I guess that is how Paris got its reputation.
Being an engineer, I started looking for picures of technology and noticed how little there was. An ox cart here and there. A few sailboats, usually fishing sloops. In the battle scenes there might be a cannon or two. But here they were in the middle of the industrial age with steam railroads, the dawn of aviation, and . . . almost nothing. A couple of trains in the distance in landscape paintings, but nothing else. Oh wait, hidden away in the corner was this little picture:
Bleriot’s little yellow monoplane crossing the English channel; one of the most significant events of early aviation history — and nothing else. And even so, the clouds and their interesting play of light and shadow are the real subject of the painting, not the airplane. And that was it; nothing from the Wright Brother’s famous exhibition in Paris. Nothing. Technology did not exist to these guys. Engineering and technology was not a fitting subject for their art work.
I thought about the great art work that I have seen at the National Air and Space Museum in Washington or in the Kennedy Spaceport in Florida. People and landscapes show up there, but that art includes our machines and what we have done with them. Even more to my liking.
Now, do I have to connect the dots for you? Art reflects what the artists think is important; great art reflects what the society thinks is important.
Yes, you can learn a lot if you travel and observe and reflect on what you have seen.
I couldn’t get to the computer yesterday to write, and thought I’d spend a very brief report on what is going on for the last couple of days.
I’m traveling with several senior NASA officials to London and Paris to have high level talks with the leaders of other national space organizations. Going into space — to the International Space Station, or sending robotic probes to obtain various scientific data, or even in the future returning to the moon and going on to Mars — going into space is international in scope. I guess what I am learning is how to work with the rest of the world.
Our first day was filled with meetings with the British government, both the executive side and the legislative side. There is quite a bit of cooperation with the British government, but they have many of the same problems and concerns that the United States has in regards to space exploration. It was very interesting to meet these folks and talk with them. I think good will come from this.
Going to the Farnborough air show was interesting. For the longest time I didn’t think we were going to get to see any airplanes fly. When I was growing up, going to the airshow meant looking at the parked planes on the ground and then seeing them fly. This airshow is all about business deals. Everybody who is anybody in the global aerospace business has a space at Farnborough. You can see everybody all at once. And we did.
We spent the better part of our day at the airshow in little conference rooms meeting with the heads of the various aerospace firms. Topics were very high level but mostly consisted in making sure that we were all working well together on the various projects that are going forward. I’m happy to pass along that the reports were good.
We managed to watch the planes fly for about an hour, and it was great. The fighters put on aerobatic shows that were phenomenal. Lots of great aircraft were there.
This morning we traveled to Paris. Straight to the meeting rooms. In one of the most beautiful and interesting cities in the world and we spent the afternoon locked in meetings with the leaders of the national space agencies from around the world. Tomorrow will be more of the same. These Heads of Agencies meetings happen about every 18 months or so. It is a chance for everybody to discuss and plan at high levels. More good meetings, not very exciting. A lot of work is like that, not exciting but very important.
Anyway we had a nice French dinner with all our international collegues. More work was done between the appetizer and the main course and by dessert some loose ends were tied up.
Whew. This is a long way from Mission Control. A lot less exciting than watching the shuttle launch. Not technical in the usual sense. But vitally important.
I’m learning a lot. Hope to get on and update the blog tomorrow but no promises.
Travel can be very educational.
Old Flight Director War Stories
We have had a splendid day in London building cooperation in space with our oldest ally. Some time later I’ll have to tell you all about it. Right now, by popular demand, I thought I’d tell a story about what happened to me when I was a brand new shuttle Flight Director. It sorta ties into some of last week’s blog and I promise it won’t be pithy or pontificate . . .
It was a DoD flight, we still can’t talk about the payload or what we accomplished, but it was my first flight and it was a high inclination flight when most of the early shuttle flights had been low inclination. High inclination means the orbit goes further north and south than usual, “inclination” being the technical term for the angle at which the orbit crosses the equator which is equivalent to the highest latitude (north or south) that the orbit reaches.
Your first flight is full of overconfidence and fear at the same time. There was a lot that the training had given me but there was a lot that I didn’t know. And was about to find out. For good reason, first time flight director’s are put on the planning shift: the crew is asleep and there is little to nothing happening in space, the flight control team on that shift is to see if any modifications are required to the pre-flight plan for the next day and get those sent up to the crew (in those days by teleprinter). I have seen many a senior flight director come in for shift change, read the flight plan updates that the rookie flight director’s team built “overnight” and throw them in the trash. It is not a confidence building experience. As a matter of fact, the Orbit 1 Team Flight Director is usually the Lead Flight Director who has been doing nothing but preparing exclusively for this particular flight for the better part of a year pre-flight. Therefore he knows more about what the objectives are and how to accomplish them than anybody else. The Orbit 1 Team Flight Director is always a senior, seasoned, experienced, Flight Director who knows the astronaut crew members personally. The Planning Team Flight Director is usually the rookie, usually assigned two months before the flight, nervous and cocky at the same time. There may be a few big egos in the Flight Director Office (that was ironic — there are lots of big egos there).
Anyway, about the fourth night, I got a call from one of the back room guys that I had only been briefed about, they never participated in the simulations. I was ready for leaks to appear in the EECOM systems (like they did on Lee Briscoe’s first flight on the planning shift), thrusters to fail off in the RCS system, IMU dilemmas to appear in the GNC systems. What I wasn’t prepared for was the etherial call over the headset from SRAG. I say etherial because most of the operators are present in the Flight Control Room. I could throw an eraser or something harder at them if they weren’t playing by the rules. But SRAG lived alone in a locked room upstairs in Mission Control. If this were the ‘day shift’ when the crew was awake, there would have been a Flight Surgeon on console and SRAG would have talked with them, but when the crew goes to bed, the Surgeons leave. Always on call, but assuming that nothing too bad can happen during crew sleep.
SRAG is about as bad as it gets. The acronym stands for “Space Radiation Analysis Group” and that is as bad a subject as you can get into. They have ‘technical methods’ that we don’t talk about. Anyway, they called and said there had been a Solar ‘event’. I love it we use euphemisms. I had been briefed on solar ‘events’ and when SRAG reported that on the Flight Loop, I almost came out of my chair. It was, as I clearly recall, about 2 AM in Houston. All the really scary things in human space flight seem to happen at 2 AM.
SRAG said they were coming down to see me in person. This is really bad. That means they didn’t want to talk about it on the Flight Loop because too many people around the world can monitor the conversations on the Flight Loop. This is bad. I spent a nervous 10 minutes chewing my fingernails as they made their way into the FCR. In hushed tones they described the problem: a major solar eruption that was sending electromagnetic radiation and highly charged particles toward the earth. Early analysis said this would exceed the crew health limits when it got to us. They advised taking no action now, they needed to do more analysis, and would be back with an update in an hour or so. Then they left the FCR. Quietly. And I was left alone with my thoughts. I pulled out the flight rules and read over the ones dealing with space radiation. The numbers SRAG predicted called for an emergency deorbit to protect the crew. This was no drill. I got on the phone and called my boss. When you are chief of the Flight Director Office, you expect to get some number of calls at 2:30 in the morning.
Lee told me to take a deep breath and call me when they came back with their analysis in an hour.
It was a long hour. Waiting.
It turned into an hour and a half. Two hours. I couldn’t stand it any more and broadcasted blind on the Flight Loop: “SRAG, this is FLIGHT, please come to the FCR”. “Be there an a few minutes, Flight” came the disembodied reply.
15 long minutes later the door popped open and the SRAG guys (they always traveled in a group) came in. In hushed tones they explained that their initial estimate had been high. More observations indicated the radiation would be lower. By this time I had memorized the radiation limit table in the Flight Rules. Now we were at the level where the flight could continue only if there were high priority mission objectives to accomplish. We were past that. But it was no longer an emergency deorbit question, maybe a deorbit the next day at the opportunity for the primary landing site. Ahh. The Orbit 1 Flight Director could make that call, and scramble the Entry team if required. Should I tell the crew? “Don’t worry them Flight, we’ll know more in a few hours”. After they left, I called my boss back and the Orbit 1 Flight Director (a couple of hours before his normal wake up time) and told them we might be looking at mission termination when the day shift came in.
It seemed like just a few minutes later when the Orbit 1 Flight Director showed up in the FCR, fully awake and dressed. He wasn’t going to let the rookie Flight Director end his mission early! He listened to my briefing, told me I didn’t know jack . . .and flew out of the FCR to the locked SRAG room and beat on the door until they let him in.
I left shift not knowing if the shuttle was going to deorbit in eight hours or not. I crashed at home after the long sleepless night. Hours later I woke up and called the MCC. No deorbit today.
On my shift the next evening, the SRAG guys had a new and lower prediction: normal mission duration would be the plan. They would have some “words for the crew” on their return. What a wild night it had been.
After the crew landed, the doc’s met them and explained that they had probably received the biggest dose of radiation ever received by a space crew. The Commander and his guys were NOT HAPPY. You never want your Commander to be NOT HAPPY.
Before the Crew debrief with the Flight Directors, the results from the onboard dosimeters were available. Nowadays those results are on telemetry and available in “real time” during the mission. But in the early days, they were only readable on the ground, post flight. The results were: . . .. normal levels of exposure. The predictions had been wrong. All of us on the ground who knew about the solar flare had been worried unnecessarily. And the crew had been furious, unnecessarily.
Later, we were briefed on improvements made to the radiation prediction tools. And the folks that study such things said it would be awfully hard to get a significant dose of radiation inside the shuttle (not hard on EVA, though) since we fly below the Van Allen Belts; even at high latitudes. Years more of study have improved our understanding, monitoring, and predicting even more.
What did I learn? A lot. But most importantly, always tell the crew. That may have been one of my first, best, lessons as a Flight Director.
True story? Absolutely. At least the way I remember it . . . .
Serendipity – Part 5
I’m going to round out this little series on the serendipity of space travel with a discussion of what we have learned about the human body in space. There are probably a thousand blogs that I could write on the serendipity of space travel so we will come back to this topic in the future.
Before 1961 the medical community was almost unanimous that space travel would be fatal to human beings. Not only would it be impossible to swallow food or water without the affect of gravity, but the circulatory system would completely break down, fluids accumulate in the wrong places and the heart would not be able to pump blood adequately.
Early flights with mammals and then primates showed significant changes and while the animals generally survived, there were serious questions. The first few manned flights were nail biters. Fortunately everybody came back alive. And some of the worst predictions were quickly shown to be false; for example swallowing is as much a function of peristalsis as it is gravity. But serious changes in the human body did show up.
For exposure to zero gravity for a week or two, the human body showed remarkable adaptation ability. But there were several close calls and many warning signs that things would not be well for longer duration flights. The Skylab flights concentrated on trying to understand some of these changes and came back with alarming results. Subsequently, many Space Shuttle flight experiments and studies refined the issues. The redistribution of fluids in the cardiovascular system, changes in the structure of the bones and muscles, all were studied in detail through many shuttle flights and most effectively on the SpaceLab Life Sciences flights.
Some of the close calls that happened in the early shuttle days have still not been widely discussed. But coping mechanisms, drug therapies, exercise protocols, and other means to control or reverse some of the physiological affects of zero gravity have been honed to a high degree. Work continues on the International Space Station with long duration solutions as the goal.
We have found out a lot about the human body in space. It is remarkably adaptable. But there are limits and countermeasures must be applied and refined.
Much of this work has application to medicine here on earth. Many of the processes that accelerate in zero gravity are like the affects of aging. Countermeasures for zero gravity can find some applications with older folks here on the ground.
Scientific journals are full of this stuff, yet it is so technical and the jargon so dense, these extraordinary findings are largely ignored by the media and thus by the general population. In medical improvements for human life alone, the space program has more than paid for itself.
Next week I am on travel and we’ll see if I can continue this blog remotely! If not, the problem won’t be with the internet but with the operator (me!). See you then, I hope.
Serendipity Part 4 – The end of all things
One of the fundamental questions of mankind is what is the fate of the universe. Hopefully its a long way off. Astronomy has always factored into cosmology and it shouldn’t be any surprise that many of NASA’s probes have studied the factors that may determine our long term outcome. Working with ground based observatories and scientists around the world, recent information has been startling.
First you have to understand that the universe is expanding. Edwin Hubble, for whom the great orbiting observatory is named, discovered that objects at great distances from us are flying away from us with a speed that increases with their distance. If you can measure their speed — which astronomers due by seeing how much the light from an object is shifted to the red end of the spectrum — you can get an accurate indication of how far away they are. The conversion factor between red shift and distance is called the Hubble constant. Edwin Hubble worked in the early part of the 20th century, this is all old news, where are we headed?
One of the big debates in cosmology is whether or not the universe is open or closed. That is, will it expand forever with the stars getting farther and farther apart until the universe suffers what some have called a freezing death? Or at some point will the universe start contracting, headed back toward that density that existed at the beginning which has been called the big crunch (opposite of the big bang)? Turns out it is almost too close to call from the observations we could make from the ground.
But we started sending probes into space. For example the Hubble (the telescope, not the astronomer) has started measuring red-shift and distance much more precisely than we can on the ground. And we sent two probes to study the background radiation lingering from the Big Bang: COBE and WMAP. And they found . . . .that the speed at which the universe is expanding is . . . (drum roll) . . . accelerating!
How can that be? Shouldn’t gravity be slowing things down? Whew. The theoreticians went to work with the data. Turns out that Einstein had it right, except he thought he was wrong. He had put a constant in one of his equations — the Comological Constant — which he later said was his biggest blunder. Now, it seems it wasn’t a blunder at all. Something is making the universe expand faster as time goes on.
Scientists can’t see it, and they can’t measure it, but the only explanation they have for this phenomenon is dark energy. Dark energy must pervade every cubic inch of the universe but we have never detected it. It must cause this acceleration; that is the only possible explanation, so they say.
Whew. Talk about finding out what you didn’t expect. So the universe won’t end in the big freeze or the big crunch but will start expanding so fast that it will end in a big rip!
I wouldn’t worry any time soon. Likely long after we’re gone and long after the earth is baked to a cinder by a dying sun.
So why do we care? Other than the academic interest, that is?
Could we do something with dark energy? I mean, if we could get hold of it. Might get more miles per gallon than gasoline! We’ve just started to figure this out. Some smart person, knowing that it is there, will figure out how to harness it.
Serendipity – Part 3
The universe is a dangerous place. Extremely energetic radiation can come from unexpected directions at almost any time.
In 1957 we knew that the earth had a magnetic field — that is the reason why compasses point to the north — but scarcely understood the implications. When the United States decided to launch Explorer 1 (after Sputnik and the Vanguard failure) a radiation detector was one of the principal instruments. Its goal was to measure cosmic rays to see if they were as prevalent above the atmosphere as predictions indicated.
After launch it appeared that the instrument periodically failed. After Explorer 3 was launched and much analysis, the investigators at Iowa State University discovered that the reason the instrument failed was that the earth’s magnetic field trapped high energy radiation in bands which came to be known as the Van Allen Belts after the leader of the team. These belts of trapped charged particles were basically unexpected. A serendipitous find.
If the Earth and Mars and Venus all formed about the same location in the solar system, they should have similar basic constituents. And so they do, except for oxygen on Earth (largely produced by plants) and water — abundant on Earth, lacking on Mars and Venus. What caused this? Both Mars and Venus have weak magnetic fields. Solar radiation strikes the top of their atmosphere basically unimpeded while the Earth’s magnetic fields deflect most of it away; only a fraction comes into contact with the atmosphere and mostly at the magnetic poles — we can see that interaction as the aurora. This radiation has the interesting property that it tends to split up molecules high in the atmosphere; H2O is broken down into hydrogen and oxygen and each constituent atom is energized to basically escape velocity. The water on Mars and Venus likely evaporated away.
We knew none of this in 1957. Some of it was suspected. How it played together has been puzzled out ever since.
The Earth has a planetary protection system. Water is the necessary ingredient for life. No strong magnetic field, no bands of trapped radiation, and your water leaves the planet. No water, no life.
It really isn’t all that simple, but that is close. Close enough for the blogosphere anyway.
Why does the Earth have such a strong magnetic field and Mars and Venus weak ones? Yet another unlooked for event. It has to do with the moon. Moon rocks are unlike almost any on earth, but in a family resemblance sort of way are like the rocks on the earth’s crust, quite different from what we think the composition of the earth’s mantle or core may be. And the crust of the Earth is considerably thinner than the crust of Mars or Venus. And the moon basically doesn’t have a mantle or molten core (or magnetic field for that matter). What is going on?
The best hypothesis — the scientific guess that best matches the available data — is that early in Earth’s history, a Mars sized planet collided with Earth and the two planets blurped together (that’s not a scientific term). Most of the heavy mantle and core type stuff stayed in what would become the Earth and most of the lighter crust type stuff got thrown off into space by the violence of the collision and subsequently coalesced into the Moon. All of this is backed up by computations, mathematical models, and lots of long scientific papers that you probably don’t want to read. And it took going to the moon and bringing back rocks and studying them in detail to make this clear.
The Earth’s large core and mantle generate the magnetic field. Venus, although almost the twin of Earth in total size and mass, does not have nearly as large a core and mantle. Poor little Mars, about half the size of Earth, with a thick crust and small core, is basically frozen. No magnetic field to speak of at either Mars or Earth.
So when you look at Earth, it really is unique among the rocky planets of the solar system. Makes you feel special doesn’t it?
We would never have known half this stuff if we hadn’t ventured off the planet, gone to the Moon, sent probes to Mars and Venus, and then thought really hard about what it means to have Van Allen Belts.
You may well ask, “so what?” This planetary protection is there and its natural and we can’t do anything about it.
Well, not exactly. But when mankind releases chemicals which punch out the ozone layer, we are affecting life on Earth in very significant ways. We stopped producing and releasing CFCs because of that damage. In the early 1960’s, the United States exploded an atomic bomb in the middle of the Van Allen Belts. Totally disrupted them for weeks. Now we have a treaty not to do that sort of thing again. Its good to know how your planetary protection system works so you don’t mess it up.
Seems like there should be a moral here . . . .
Oh yeah. Going into space has allowed us to find out things that we didn’t have any idea about — and which are really important to our continued survival.
Serendipity — Part 2 – a warning
From the Merriam-Webster On-Line Dictionary:
Serendipity ser·en·dip·i·ty Pronunciation: -di-pə-tē noun Etymology: from its possession by the heroes of the Persian fairy tale The Three Princes of Serendip 1754
: the faculty or phenomenon of finding valuable or agreeable things not sought for; also : an instance of this
Sometimes, when you look you find out things that you never expected to find. Unfortunately, sometimes what you find out is not always agreeable; but maybe necessary. Forewarned is forearmed, so the saying goes. Dr. John Horack of Marshall Space Flight Center’s Science and Mission Systems office alerted me to an unusual discovery made by NASA in the jungles of Guatemala.
This is the story of a series of satellites and the ground based analysis of their data. First of all, the satellites were not constructed to be an archeological tool. They were intended to monitor many things on the earth, in particular plant growth to help understand how agriculture and forestry could be improved. To do this, the instruments lofted into space looked at various spectral bands in ways the human eye cannot see. Flying over the Peten basin of Guatemala in the dry season, they collected data which amounted to plant health. Ground processing with intricate computer codes extracted patterns from the raw data. And these patterns meant something very interesting.
The Maya created a great civilization that lasted the better part of a millennium. At the time they were unsurpassed in astronomy and mathematics, especially when compared to Europe, deep in its dark ages. The Maya were on par with the great Arabian scientists and philosophers of the same era whose algebra is still bedevils schoolchildren. The Mayan empire stretched across meso-america and their influence was felt by all peoples for a thousand miles north and south.
But their civilization suddenly collapsed. We don’t really know why. Just collapsed. No record of a war, perhaps it was a plague, but nobody knows. Most of the Mayan ruins lie in the all but impenetrable forests of central America. Archeologists suspect that as late as a decade ago, less than 1% of the Mayan ruins had been studied. The Peten basin was the nexus of their homeland, today it is largely uninhabited and wild. In the middle of what amounted to a resource desert, the Maya had built a huge concentrated metroplex. The population density exceeded that of the most populated areas of China or India today. Food production, water distribution, waste management were all the subject of intense planning and construction. Until the day it was all abandoned.
Ground processing of satellite data during the region’s dry season detected subtle spectral differences in signatures from the canopy tops. In regular patterns some of the flora was more stressed — imperceptible to the human eye — than the surrounding vegetation. With GPS precision, archeological teams were sent to some of these places and discovered — ruins: aqueducts, buildings, temples, homes — an entire civilization mapped precisely by the change their foundations made to the soil.
Recent computer modeling of the local climate may give some clues as to why this happened. In the natural cycle there are periods which are drier and periods which are wetter. With proper understanding and accomodation, humans have dealt with such cycles with reasonable inconvenience. However, when the dry cycle hit central America in the 9th century, the Maya had deforested the entire region. The computer models predict that temperatures rose significantly than would have been the case if the vegetation had been intact. The hydrological cycle was interrupted because the moisture naturally exhaled by trees. The models show the rains didn’t merely diminsh, they quit altogether. Food production must have collapsed; the water system must have dried up when the reservoirs were no longer refilled. Civilization as the Maya knew it came abruptly to an end. And the people either died or walked away.
When the European explorers came 500 years later, the Maya still existed in small pockets, but they were no longer a great civilization; just another native tribe which was swept away with the others.
So what is the lesson for us? There is a lot of debate about global climate change these days. I don’t know what you think about global climate change — is it happening or not, is it man made or not — and perhaps that debate is extraneous to the central history lesson of the Maya. Here is the lesson: if you don’t understand what you are doing to your neighborhood, bad things can happen. Really bad things. So learn, understand, and adjust accordingly.
If we don’t learn anything else from the collapse of the Maya, that is probably enough.
And nobody foresaw that we would figure this out by sending satellites into space.
Serendipity — with a warning.
You can read more about it here: