Living in the Universe

NASA and the Race for Space

Fourth Week of February 2007

This week saw the appearance of an interesting Op-Ed piece in the New York Times, written by Carolyn Porco. Carolyn is a planetary scientist, and a leader of the Imaging Science team from the Cassini mission, and also the director of the Cassini Imaging Lab for operations. I’ve known her for quite a while; she’s a great and eloquent spokesperson for planetary science and astronomy in general. She has some strong views, and they’re beautifully articulated in her Op-Ed piece.

Her topic is NASA’s commitment to the space program and to planetary exploration. I’ll quote from her article at times. She starts by saying, “After years of spending our nation’s space budget building an orbiting space station of questionable utility, serviced by an operationally expensive space shuttle of unsafe design, NASA has set a new direction for the future of human spaceflight. Once again we have our sights set on the Moon and beyond. We are finally boldly going to make our way into space, this time to stay.” She follows with, “It is an opinion long and widely held within the space exploration community that the Nixon administration’s termination of the program that built the Saturn V moon rocket was a gargantuan mistake.”

This is her premise of her piece, but it’s not a universally held view. Some planetary scientists and astronomers believe that the Moon, Mars, and Beyond mission set by president George Bush and guiding current NASA direction is a diversion from planetary exploration in astronomy, but Carolyn makes an excellent point. She starts with the fact that the Saturn V was the largest and most powerful launch vehicle the U.S. has ever built. It had a launching capacity more than five times greater, and a developmental cost twenty-five percent lower, and a build-to-operate cost less than half of today’s space shuttle. It was a good capability, and we let it lapse.

Why? For essentially political reasons. We renounced the Moon, abandoned Apollo and the Saturn V, and retreated into low Earth orbit where, as she puts it, “We spent the last twenty-five years going around in circles.” That’s nice phrasing. “The cost to the nation of this misstep,” she continues, “is enormous. For starters we lost an investment, adjusted to current day dollars, of a hundred and sixty billion. That was the cost to get to, land on, walk on, drive on, and otherwise explore the Moon. About thirty billion of that was the cost of the Saturn V.” She also points out that the protection facilities for Saturn V and its other lunar exploration components were lost, and we lost the technological means for deep space exploration.

What we put in place of Apollo has gotten us nowhere fast. A majority of astronomers and planetary scientists are agreed on that. The International Space Station is space pork unbeloved by scientists, could have been built with only half a dozen Saturn V launchings instead of the more than two dozen shuttle trips that will be required to finish it. She also points out that the termination of Saturn V had a stifling effect on robotic exploration of other planets because we lost the ability to deliver larger and in some cases faster payloads elsewhere in the solar system. “In the end, instead of having a ubiquitous presence throughout the solar system, humans haven’t set foot on the Moon for thirty-five years, and even our robotic explorations in that time have been throttled because we deliberately reduced our access to deep space.” To continue quoting her, “Today, however, NASA is again looking up and out. Vigorous efforts are underway to complete the space station in order to fulfill international commitments that would be unwise to violate. When that’s done, the plan is to retire the space shuttle in 2010 in favor of a new program to return to the Moon with a party of humans by 2020. The mainstay of this program is the Aries launching system, capable of sending sixty-five metric tons to the Moon, exceeding the capacity of Saturn V by more than forty percent.”

Porco is a strong supporter of the Aries launch capability because she thinks it will get us back to where we were when we had the Saturn V. She says, “Forty-five years ago John Glenn became the first American to venture into orbit. Just nine years old, I knew at that moment the future would be big and wide, and I might go places no one has ever been before. There could be no better way to encourage an equally optimistic belief in the future than to embark on an odyssey that presents tremendous challenges, demands rigor and discipline, requires decades-long focus, inspires international cooperation, promotes lasting peace, improves life for all, and paints a stirring vision of an expanded human presence beyond the Earth. There could be no better way to say the future is boundless, and it belongs to us.”

Those are indeed inspiring words from Carolyn Porco. Another perspective of course was that Apollo was a pinnacle and a logical endpoint. It’s based on chemical rocket technology where ninety-five percent of the mass is used to send a tiny payload on its way. Chemical rockets are essentially huge fireworks, and they’re grossly inefficient. Another viewpoint on the space program is that we’ve been stifled by the fact that only one government has been playing this game, especially in the last decade since the demise of the Soviet Union. It would have been better perhaps to explore alternative propulsion systems and not be so conservative in our one use of chemical technology.

Government regulation amounts to government monopoly. The private sector is finally beginning to flex its muscles and entreprenurial prowess. The government is simply inefficient in some of its research programs and NASA is no exception. There’s an upside and a downside when the private sector gets involved. Commercialization of space introduces a profit motive, and we all know that tacky and sleazy forms of advertising can result from that. On the other hand imagine what would happen if you gave a visionary like Burt Rutan, the guy who built the machine that won the X Prize for only about a hundred million dollars, a NASA-like budget of billions of dollars. I think it would be spectacular. We need different ways to approach the space issue and accelerate our progress. If we’re bold, the future is indeed bright.

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Mapping the Red Planet

Third Week of February 2007

Mars is in the news once again, and it’s all about water. Scientists have long debated whether water flowed on the red planet, and the evidence has been increasing steadily in recent years. The presence of water would increase the possibility of at least some form of subsurface life existing on the red planet. This past week images from a camera aboard NASA’s Mars Reconnaissance Orbiter have showed a region of alternating layers of dark and light toned rock in a giant rift valley. Within the deposits are a series of linear fractures called joints that are surrounded by halos of light toned bedrock.

This work was done by a team at my university, the University of Arizona, and their findings have just been published in the journal nature. Their lead author Chris Okubo says, “The halos indicate areas where fluids, probably water, pass through the bedrock. Minerals in the fluids strengthen and bleach the rock leaving some areas more resistant to erosion than others.” He says, “On Earth bleaching of rock surrounding a fracture is a clear indication of chemical reactions between fluids circulating within that fracture in the host rock.” The researchers also said that layered outcrops can indicate cycles with materials deposited by regular episodes of water, wind, or volcanic activity.

You’ll recognize that this evidence is not completely direct. It’s based on the interpretation of geological features, evidence that is always slightly suspect because there may be alternative explanations. But these are experts not only in planetary geology but in terrestrial geology, and there’s no question that the features they’ve identified are most easily explained by water.

Just last December scientists reported that water may be flowing through Mars’ rigid surface when the Global Surveyor showed changes in craters providing evidence that water moved through them as recently as several years ago and may be doing so now. The Surveyor had previously spotted tens of thousands of gullies that scientists believed were geologically young and carved by fast moving water coursing down cliffs. That water eventually freezes and quickly evaporates. Liquid water cannot exist on the surface of Mars right now. But it can be spurred from interior activity, and it could exist under pressure under the surface. In addition, two craters in the southern hemisphere that were photographed in 1999 and 2001 were examined again in 2004 and 2005, and the images showed changes consistent with water flowing down the crater walls.

The summary of all this is that, as with the case of global warming, another topic in the news recently, there’s steadily accumulating evidence for water, evidence that cannot really be refuted. Each individual piece of evidence may have an alternative explanation, but taken together they are starting to make a compelling case for water at some times under the Martian surface. And where water goes, we think that life follows. That’s the big speculation. So we are itching to get back to Mars and see what’s really happening.

A second piece of news on Mars in the past week was the release of data from the HRSC experiment aboard ESA’s Mars express. This spacecraft has produced what are called the first hiker’s maps of Mars giving detailed high contours and the names of geological features. These maps are going to become the standard reference for future Martian research. They’re being called topo maps because they use contour lines to show the heights of the landscape. They are taken by a high-resolution stereo camera which gives the altitude information. On Earth the same kind of maps are used by hikers and planning authorities. They are called ordinance survey maps in the U.K. where I come from.

The researchers chose the Iani Chaos region for the release of these first maps because of its major topographical interest. It’s covered in huge blocks and hills that form a chaotic pattern across the landscape. These islands of rock are likely all that remains of a previous surface of Mars. The areas in between the islands collapsed when cavities formed below the surface. Initially these cavities may have been supported by the presence of ice which melted due to volcanic heat. As water flowed out to the Ares Vallis towards the northern lowlands of Mars the landscape collapsed and formed the Iani Chaos region we see today. This is not geologically recent; some of the activity happened over a billion years ago, but it’s yet more evidence for ancient water on the surface of Mars.

Topo maps are a demonstration of the kind of tools that we will need when we go back to Mars for detailed exploration. The HRSC is on the way to providing enough data to create such maps over the whole of Mars, over ten thousand particular map sheets, each covering an equal area of the Martian surface. The majority of the maps will be on a scale of one to two hundred thousand. That’s a resolution of ten meters, meaning all features about the size of a large room will be identified. Particular interesting regions will be surveyed to a scale of one in fifty thousand meaning everything larger than two meters, about the size of a sofa, will be identified. This kind of detail is really required to send spacecraft to Mars with the best possible information, and such spacecraft are coming. There will be a virtual armada of spacecraft heading to Mars in the next five to ten years.

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Fire, Ice, and Earth’s Oceans

Second Week of February 2007

This week saw an interesting story about conditions on the early Earth and the way in which the Earth managed to be hospitable for life in its first billion years. Earth is subject to something called the Faint Earth Paradox. It’s been habitable for four billion years, but the early Sun was twenty-five to thirty percent dimmer than it is today. And with the distance the Earth is from the Sun, that should have been enough to freeze it over, and yet life existed in this early part of the Earth’s history.

Geologists and paleontologists are trying to understand how that might have happened. This recent study finds that carbon dioxide, the greenhouse gas that’s now become a bane of life for modern society because of global warming, may have saved the Earth from freezing over early in its history. Scientists have theorized for years that high concentrations of greenhouse gases could have helped the Earth avoid global freezing in its youth, by allowing the atmosphere to retain more heat than it’s lost. But now a team from the Universities of Chicago and Colorado have analyzed ancient rocks from the shores of Hudson Bay in northern Quebec and found the first direct field evidence to support this idea.

The study shows that carbon dioxide in the Earth’s atmosphere could have sustained surface temperatures above freezing before 3.8 billion years ago. Previous studies had shown liquid water existed at the Earth’s surface, even though the weak Sun should have been unable to warm the planet above freezing condition. These ancient rocks from Quebec contain carbon and iron carbonates believed to have precipitated from the ancient oceans. Since iron carbonate could only have formed in an atmosphere containing much more carbon dioxide than found in Earth’s atmosphere today, the researchers concluded that the early Earth’s environment was rich in carbon dioxide. Lead scientist Steve Mojzsis of the University of Colorado said, “We now have direct evidence the Earth’s atmosphere was loaded with carbon dioxide early in its history which kept the planet from freezing and going the way of Mars.” The carbon dioxide could even have acted as a planetary thermostat, since cold, icy conditions on Earth would have decreased normal chemical weathering of rocks and increased the amount of carbon dioxide moving into the atmosphere, ratcheting up Earth’s temperature.

A companion paper shows talks about the technique they used, based on what’s called uranium-lead dating, the decay rate of radioactive elements contained in tiny zircon crystals. The CU Boulder team analyzed the rocks by crushing them into powder and dating zircon crystals present in the rock. This technique allowed them to calculate the geological age of the crystals based on the radioactive decay rate of the uranium and lead isotopes in relation to each other. This technique is accurate to one percent. As Mojzsis says, “Zircon is nature’s best time keeper.” The tests showed that the rocks in Quebec are roughly 3.8 billion years old, about the same age as the other oldest outcropping known in west Greenland.

This important work has given us a reason to understand how the life on Earth could have been hospitable over four billion continuous years of its history. You may also recall that a few years ago a zircon crystal provided the evidence for the oldest rock yet found on Earth, although not evidence for life necessarily. The same team from the University of Colorado, this time working in Western Australia, were able to find zircon crystals 4.4 billion years old. That’s a short hundred and fifty million years from the formation of the Earth itself, so those are the oldest rocks yet known.

A second study this week from the University of Washington gives us a sense of the strangeness of life in the deep-sea ocean. It’s a story about noises of the deep. Right now there are some enormously varied and wide ecosystems that exist on volcanic ridges one or two miles below the surface of the Earth where the Sun never shines. It’s pitch black, but what’s that rumbling? It must be one of those pesky black smokers. Those babies can fry your face off, as superheated water charges out of a volcanic vent. The long-held assumption that black smokers were silent is apparently wrong.

It’s prompting scientists to wonder, could the sound and vibrations of black smokers be the reason that fish living in total darkness avoid being poached by water as hot as seven hundred and fifty degrees Fahrenheit, and might similar signs guide them to the smorgasbord of tubeworms, muscles, shrimp, snail, and other fauna at vents with more temperate waters?

Hydrothermal vents were discovered in the 1970s along volcanically active ridges where seawater seeps into the seafloor, picks up heat and minerals, and vents back into the ocean depths. The hottest and most violent of these vents are called black smokers because when the fluids they emit hit the icy cold seawater, minerals in the fluid precipitate out, and it looks like dark, billowing, smoke underwater. It had been suspected that the vents were silent, but a number of scientists suspected the vents could be generating sounds so new recording devices were used to test this assumption. Funding from the Keck Foundation was used to build a deep-sea digital acoustic recording system and drop it close to a vent in the Juan de Fuca ridge about an hour off the coast of Seattle. The researchers recorded dozens of hours of sound at a vent that scientists had called Sully and another hundred hours at a vent called Puffer. They likened the sound of these vents to the rumbling of an avalanche or forest fire. If you were sitting a foot away it would sound like a very loud conversation. You would unfortunately be dead because the pressure is so high you would implode.

Four mechanisms might be causing the noise. The flow could be pulsating its volume as the waters cool. Dissimilar fluids in the flow could mix and generate noise, or fluids rushing through the nooks and crannies of the smoker vent itself could be creating noise. Buried within the rich sounds that produce the rumbling, the analysis also found some surprising resonant tones which could be caused by a number of things. Flows along the bumps and cavities inside vent structures could cause tones, in the same way jug band members produce sound by blowing across the mouths of their jugs causing the air inside the jug to resonate and produce a deep tone. Both the Sully and Puffer vents produce resonant tones at several different frequencies that we can’t discern with all the other noise, but perhaps some of the creatures that live in these environments can discern them. If fish are actually using the sounds to navigate, distinctive tones may be how fish find their way back to cooler vents where the eating is particularly good.

It’s fascinating work, and it leads to the supposition that life adapted to a deep sea environment that have sensory apparatus quite different from our own. Hydrothermal vents are also the best model we have for what might be found deep under the icepack of Europa, the giant moon of Jupiter, where we hope to go one day and find evidence of extrasolar life within our own solar system.

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The First 200 Exoplanets

First Week of February 2007

This week saw an exciting story coming from the Hubble Space Telescope where astronomers have studied for the first time the layer cake structure in the atmosphere of a planet orbiting another star. What Hubble found was a dense upper layer of hot hydrogen where the super hot planet’s atmosphere is bleeding off into space.

The planet, which has the unevocative name HD 209458B, is unlike any world in our solar system. It’s a hundred and fifty light years away in the constellation Pegasus. It orbits so close to its star and gets so hot that its gas is streaming into space making the planet appear to have a comet-like tail. This new research, by a team based at the University of Arizona, reveals the layer in the upper atmosphere of the planet where the gas becomes so hot that it escapes like steam rising from a boiler. According to Gilda Ballester, a member of the team, “The layer we studied is a transition zone where the temperature skyrockets from thirteen hundred degrees Fahrenheit to about twenty-five thousand degrees which is hotter than the surface of the Sun. With this detection,” she said, “we see the details of how a planet loses its atmosphere.”

The intense radiation from the star heats the gas in the upper atmosphere and inflates it like a balloon. The gas is so hot that it moves very fast and escapes the gravity of the planet at a rate of ten thousand tons a second. That’s more than three times the rate that water flows over Niagara Falls. The planet, however, is large enough that it’s not going to wither away any time soon. Even at this rate of mass loss astronomers estimate its lifetime to be more than five billion years. The scorched planet is like a puffy version of Jupiter.

In fact it’s one of a set of planets called “hot Jupiters,” exoplanets that orbit very close to their parent stars. The planet completes its orbit in three and a half days and is only five million miles from its host, which is twenty times closer than the Earth is to the Sun. For comparison, Mercury, the closest planet to our Sun, is ten times further away than this planet is from its star. Unlike this planet, however, Mercury is a small ball of iron with a rocky crust. Although this extrasolar planet does not have any twin in our solar system, it has plenty of relatives. About ten to fifteen percent of the more than two hundred known extrasolar planets are hot Jupiters. That’s about two dozen of them. HD 209458B is one of the most intensely studied of the 200 exoplanets because its one of the very few alien worlds that can be seen passing in front of or transiting its star causing it to dim slightly.

To see how important this is let’s review what we do and don’t know about the two hundred extrasolar planets that have been found so far. Almost all of them have been found by the Doppler technique. It’s an indirect technique where the planet is never directly observed, but in fact we observe the star and detect the tugging of the parent star to and fro by the massive planet. The Doppler method only yields the mass of the planet and even then only roughly. We learn nothing else about the planet that orbits the star.

To learn more, such as the size and structure, and even the composition of the planet’s atmosphere, we need to be lucky. We need to be in a situation where the alignment of the planet orbit causes it to pass between us and its parent star creating a transit, a momentary dipping of the light of the star as the planet crosses the face of the star. Only fourteen extrasolar planets have transits, so this is one of a very small category. In fact, hot, close planets to their stars are most likely to transit because the geometry is favorable for that kind of an event. HD 209458B is a rare object, and it’s been heavily studied because it is so rare.

This dimming, or transiting, gives us an extra handle on how the planet is arranged because with timing we can watch the planet eclipsing and then being eclipsed by the parent star, and by careful observation we can learn what it’s made of using spectroscopy and how large it is by the rate at which the planet dims. The planet transits have been used to measure the chemical composition of this planet’s atmosphere. HD 209458B was first studied in the year 2003 with the Hubble Space Telescope’s Imaging Spectrograph. A team led by David Charbonneau found heavy elements in the atmosphere of the planet: oxygen, carbon, and sodium.

The more recent research is essentially using archival data and digging out more information based on the hydrogen in those spectra. Learning that we can do this with spectra taken from the Hubble Space Telescope is a little bittersweet, because last year the spectrograph used to make these and other important observations died, and last week astronomers were also saddened when the Hubble Space Telescope lost its major workhorse instrument, the Advanced Camera for Surveys. In fact, this camera had just been used to find sixteen hot Jupiters in the central regions of the Milky Way galaxy. Hubble has lost much of its capability and remains in an awkward limbo until its planned servicing mission in October next year, but this exciting discovery reminds us of what will be in store when we gain the ability to take spectra in Earth orbit.

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