We Should Become Martians: Part I. ~ Guest Blogger Claude Plymate Returns!

  Claude Plymate is the Telescope Engineer/Chief Observer at  Big Bear Solar Observatory in California, and is the  former chief  wrangler of the McMath-Pierce Solar Telescope at Kitt Peak National Observatory Arizona for many years. He is a regular contributor to Musical Milliner.

It likely won’t come as any surprise to those of you who know me or have read some of my earlier essays that I am a strong advocate of sending humans to Mars. What might surprise you are my reasons which are more about societal needs than about scientific exploration. Our population has now passed the 7 billion mark.

There are indicators all around us that this planet cannot maintain the pressure we’re applying to its resources and resiliency. There is little reason for me to go into the details here; you are all well aware of the risks we are subjecting ourselves to. Global climate change, fresh water depletion, famine, nuclear proliferation, pandemics and war are just a sampling of the dangers we pose to ourselves. On top of our self-imposed hazards, the solar system is in general a menacing place to live.  Asteroid impacts have already wiped out the dominant species on Earth at least once before.  A nearby supernova could disrupt our ozone layer with catastrophic consequences. We are fortunate to have a strong magnetic field and atmosphere that protects us from the harsh radiation coming from solar flares but civilization has left our technology quite vulnerable to such eruptions. It doesn’t appear that a “super flare” will kill us outright but just imagine the disruption to society if the Internet, electric grid, GPS system, radio communications and even telephones suddenly and unexpectedly went ‘dark’– and not just for a few hours but possibly days, weeks or even months!

What I’m trying to point out is that there are many real threats to our civilization and even our existence as a species. Some are self-imposed, some are natural.

This leads us to the question of how to mitigate such threats to humanity.  Consider how you deal daily with risk management of other items you regard as valuable. For example, you wish to protect your documents and photos stored on your computer’s hard drive. What do you do? Of course, you backup your files onto a separate drive stored  in a separate location. (You do back up your files, don’t you?)  Applying this same rationale to society naturally leads to the conclusion that to survive long-term, humanity must expand beyond this one little planet.  Then, even if the unthinkable occurs, all that humanity has achieved won’t completely disappear from history.

The obvious first destination for a human outpost beyond Earth is Mars. Mars is the most Earthlike of the other planets within the solar system. It is close in astronomical terms and has an atmosphere. Mars is a place we can live. Plus, the lower surface gravity of Mars (about 1/4  that of Earth) makes getting on and off its surface much easier than here on the Earth.

Unfortunately, the atmosphere on Mars is very tenuous with a mean surface pressure ~ 600 Pa (0.087 psi), equivalent to an Earth atmospheric altitude of around 90,590 ft (27,612 m). On top of that, it’s a toxic mixture of mostly carbon dioxide. Anyone on the surface would have to wear a pressure suit (space suit). Even this exceedingly thin atmosphere could be used to pressurize suits & shelters. All that would be needed would be a compressor to pressurize the interiors. Simple inflatable structures could even be used for such things as storage, workshops and greenhouses. You still couldn’t breathe in the high CO2 environments but an oxygen mask would be all that’s required for people to work in otherwise shirtsleeve comfort. There are likely many plants that could thrive in these pressurized greenhouses. Obliviously, living quarters would need more oxygen to make a breathable atmosphere which is easily attainable
by liberating O2 from either CO2, water or even iron oxides (rust!) in the soil that gives the planet its red color.

Water means life. We need water to drink, water for crops and water to make oxygen. Recent Mars probes are making it clear that water (at least in the form of ice) is much more common on Mars than previously believed. What is required to harvest the water is energy; energy to drill wells or mine ice, energy to extract the O2. Possible sources for power include solar panels and/or nuclear generators and perhaps even geothermal. I suspect that the atmosphere is simply too thin to support wind power.

There are two primary arguments against going to Mars that people normally state; interplanetary spaceflight is beyond our technical ability and the cost would be far too great. I’d like to address these arguments one at a time.

Stay tuned for We Should Become Martians: Part II next week.


Life in the Universe, Part III~How to Find a Planet

Guest writer astronomer Claude Plymate, chief wrangler of the McMath-Pierce Solar Telescope at Kitt Peak National Observatory, lets us in on some fascinating facts. Geek or non, you will enjoy Claude’s latest installment

                  How to Find a Planet

Imagine gazing at an extremely bright light bulb on a dark night with a 1 mm diameter ball bearing placed about 40 feet away from it. You can probably appreciate that the blinding light would make the ball bearing all but impossible to see. Now imagine looking at the light and metal BB from a distance of about 2000 miles away. Believe it or not, the tiny angle (0.77 arcseconds) between light bulb and BB can be easily resolved in modern telescopes but the dim little BB would be completely lost in the glare of the intense light source. This is what it is like to try and spot an Earth sized planet orbiting a one of our nearby stellar neighbors. Most stars, however, are much farther away making it that much more difficult to spot any potential orbiting planets. Hunting planets around other stars is hard work! It is quite a testimonial to human ingenuity that, despite the difficulty, as of this writing over 1700 planets have been discovered orbiting stars other than our Sun! To find these extrasolar planets, or “exoplanets”, astronomers have tried various techniques with varying levels of success. Only two techniques have so far proven to be very successful.

The Radial Velocity or “Wobble” Method

It’s not quite correct to say that the Earth orbits the Sun. Technically, both the Earth and Sun orbit about the center of mass of the of the Earth-Sun system. Picture a hanging mobile sculpture, the Sun on one side and the Earth on the other with a stick between them that the whole system is suspended from. Since the Sun is much bigger and heavier than our little Earth, the mobile is suspended from a point close to but not centered on the Sun. When you spin the mobile, the planet sweeps out a large arc while the large Sun moves just a little.

The same is true for orbits. Planets swing around in their orbits, all the while gravitationally tugging on their host stars. A planet’s star reacts to this tug by circling around the balance point between them just like with the spinning mobile. Since stars are so much more massive than their planets, the radii of their orbits are correspondingly smaller. The point about which the star orbits is normally well inside the star itself!

Viewed from above – face on to the orbital plane of the stellar system – an orbiting planet will cause its star to wobble ever so slightly, like a boat rolling over waves, as it drifts through the galaxy. Astronomers spent decades carefully measuring the positions of the closest stars in our celestial neighborhood. Try as they might, no deviations in any star’s path due to a planetary system was ever detected. Either the perturbations were too small to measure or there simply weren’t any planets out there tugging on the stars.

Then, starting in the late 1980’s, astronomers tried a different approach. Instead of looking for the side-to-side wobble imposed by a face-on orbital system, they decided to use the in-and-out (radial) motion induced by an edge-on planetary system. If our vantage point happens to be more-or-less in the orbital plane of a star’s planets, the star will appear to move towards us half the time and away the other half of the time. A star’s radial (in-and-out) motion might seem like a more difficult measurement to make compared to simply plotting its zig-zag motion across the sky, but believe it or not, up until very recently (see the Photometric Method below), this is how the vast majority of extrasolar planets have been found. At the time I’m writing this, the total of number of planets found with the radial velocity method is 531!

How can astronomers measure such small radial motions in stars that are many light-years away? Spectroscopy. You are likely familiar with the fact that astronomers have long used “red shifts” of spectral features in distant galaxies to measure their “Doppler” velocity. A close look at any star’s spectrum (it’s rainbow of colors) reveals a plethora of gaps or dark lines breaking up the continuum. These “spectral lines” are due to the various gasses that make up its atmosphere. Every type of atom and molecule absorbs light at numerous precisely known wavelengths (colors). The star’s spectrum is then the combination of all the spectra of the gasses that make it up. Stars can then be categorized by their “spectral signature” – sometimes likened to a stellar barcode.

The radial velocity of a star or galaxy causes its entire spectrum to shift towards the red (longer wavelengths) if moving away from us or towards the blue (shorter wavelengths) when coming nearer. (This is how it was determined that the Universe is expanding. Hubble – the guy not the telescope – found that the farther away a galaxy is, the greater its red shift velocity tends to be. His conclusion that the Universe much be expanding was one of the major discoveries of the 20th century.) The same phenomenon is experienced with sound waves whenever a fast moving vehicle zips past making that characteristic Eeeeeeeeooooooooo sound.

We can easily distinguish that tonal shift in sound from relatively slow moving vehicles because the speed of sound itself is relatively slow (~349 m/s). The speed of light, however, is MUCH faster (~300,000,000 m/s), about 860,000 times faster! The Doppler shift seen in light is exceedingly small for slow moving objects. Still, by the 1980’s spectrographs had reached the exquisite resolution and stability required to measure the slow back-and-forth velocities of stars do-si-doing with their planets – at least their BIG planets! Small planets like the Earth are still beyond our detection limit.

Early detections were of strange so called “Hot Jupiters”, that is big planets orbiting very close to their stars. These planetary systems didn’t much resemble our solar system with its small terrestrial planets in close and the big gas giants farther out. We’d always assumed our solar system is rather typical. Is this not the case or might this simply be a “selection effect?” The bigger the planet the larger its influence on its star. Likewise, the closer the planet is to its star, the larger the perturbations of its parent star will be. So, the radial velocity method is most sensitive to big, close in planets. It’s of little surprise then that that is what we see! The farther a planet is from its star, the longer its orbital period. Finding smaller planets that are farther from their star, therefore, takes more spectral resolution and more time. To succeed in this business, you have to be both obsessively precise and patient.

Once the period of a planet’s orbit and its star’s mass (found from its spectral class) are known, determining the lower limit of the planet’s mass becomes a trivially simple calculation. The calculated mass is only a lower limit because we don’t know if we are looking truly edge-on to the stars back-and-forth motion or at some skew angle. Any deviation from straight-on will diminish the motion along our line of sight. To absolutely measure the size of a planet relative to its star takes…

The Transit or Photometric Method

Occasionally, by happy coincidence, we happen to be precisely aligned along the axis of an exoplanet’s orbital plan such that we see the planet transit across the disk of its star. This creates a mini-eclipse which ever so slightly dims the light we receive from that star. By plotting how much the star is dimmed, the relative size of the planet compared to its star can be calculated. Such measurements are known as Photometry (“photo” meaning light plus “metry” meaning to measure, is the measurement of light).

The axes of planetary orbits around stars are randomly distributed. They can be tipped at any angle from face on (looking down from above or up from below) to edge on where the orbital axis cuts right across the star. A planet the size of Earth at its distance from our Sun makes a really small target. For the Earth to appear to cut across the Sun as viewed from far outside the solar system, the viewing angle would have to be within about +/- 0.3 degrees of our orbital axis. From a random position, the chances of this are only about 1 in 300. To have a good chance of catching some planets that transit across the disk of their stars, you need to observe a LOT of stars! Also, remember that the Earth takes a year to go around the Sun.

To catch a transit of Earth from our imaginary vantage point outside of the solar system, we’d have to watch for a year to see just one transit. To be sure that what we saw was a planetary transit and not some random even (Sun spot, a random star moving across the primary target star, equipment problem, etc.), we’d need to see at least a 3 transits. And in the case of the Earth, this would take a minimum of 3 years. If you see a star dim once, you can’t say what caused it. If you see it happen twice, it’s always possible that it was caused by two separate objects. Seen a third time, you can be confident you know that it’s something in a regular orbit and you know what that orbital period is. So, not only do you need to observe a lot of stars but you need to watch them for a long time – at least several years!

Enter Kepler. Kepler is a NASA spacecraft that was launched in March of 2009. Its mission is to continuously stare at one area of the sky between the constellations Cygnus and Lyra. The spacecraft continuously monitors around 100,000 objects in a roughly 10×10 degree field of view. Being in space, Kepler does not have to contend with the shimmering fluctuations and weather variability of our atmosphere. This gives it an undisturbed and exceedingly stable vantage point resulting in unsurpassed sensitivity to stellar brightness variations. The Kepler science team recently announced more than 1200 candidate planets have been seen transiting stars in its field of view! On top of that, 54 of these planets appear to be at the right distance from their stars to be in the “habital zone” where planetary temperatures can allow liquid water to exist! Assuming these all pan out, this represents a huge jump in the number of worlds we now know about. This first list of exoplants is only the tip of the Kepler’s iceberg based on its first year of observations. We can expect many more discoveries to trickle in as Kepler continues its mission over the next few years.

Although Kepler’s transit approach to exoplanet detection is proving to be remarkably prolific, the method can’t tell us all that we’d like to know about the planets its finding. For this, other methods will need to be employed. Eventually, we should have telescopes that will be able to capture the spectrum of the planets themselves. A spectrum can tell us what makes up the planetary atmospheres. I don’t know when it’ll happen but someday we’ll hit pay dirt when oxygen and other molecules formed by biology are found in the atmosphere of an exoplanet. That will be the day when we indisputably learn that the Earth is not alone and unique in this galaxy. We will finally know that we have kindred among the stars and that life thrives throughout the Universe.

(c) GoshGusPublishing (ascap) 2011

Life in the Universe~Part II: The Drake Equation

In Part I of this essay, we looked at how common life might be outside of the Earth. The only type of life considered was microbial life. Most of us, however, are really interested in more advanced life forms – the type of critters we could sit down with, have a cup of coffee and discuss the meaning of life with. Unfortunately, there appears to be a vast chasm between microbe and ET. Single celled creatures appeared very early in the Earth’s history, more than 3.8 billion years ago – not long after the Earth had cooled enough to allow for liquid water. It appears that, given a well-suited environment, life can get started fairly quickly. Those early microbes thrived. After that, however, it took another 2 1/2 billion years before the first multi-cellular life appeared. It was that innovation that really seemed to set us on the evolutionary path toward ever more complex and advanced life forms. That long 2.5 billion year gap between single- and multi-celled life seems to indicates that the jump from simple to more complex life is much more difficult and unlikely than the start of life itself! Even if life is exceedingly common among the stars, complex life might still be a precious rarity.

Even when advanced life does eventually develop, how often does evolution lead to intelligence? While advanced forms like worms and bamboo are very cool, I want more. I want something I can talk to, ask questions of and maybe even learn from. There are innumerable species of plants and animals growing on or roaming this planet but only a handful are thought of as possessing intelligence. Each species develops its own strategy for survival. Some are fast, some big, some stay well hidden and some are just plain mean. Only a handful of animal species appear to have experimented with intelligence. We know that feeding a big hungry brain takes a lot of resources. If it isn’t really advantageous to have one, you’re not going to evolve one. Other survival strategies than intelligence have proven to work very well and don’t require all the resources consumed by that hunk of meat you carry around between your ears. Look at ants, cockroaches or crabgrass; all very successful but far from what we think of as smart. Arguments like these lead me to believe that intelligence is quite uncommon even among complex life forms.

How many intelligent species are then likely to inhabit our galaxy? To try and get a handle on our level of knowledge (or ignorance) concerning this question astronomer Frank Drake (currently with the SETI Institute) developed a simple equation way back in 1961 that details the factors that contribute to the current total number of intelligent civilizations. The equation has come to be famously known as The Drake Equation:
N = R* x f(p) x n(e) x f(l) x f(i) x f(c) x L
The variables in the equation are defined as:

R* – the average rate of star formation in our galaxy (stars per year).

f(p) – the fraction of stars that have planetary systems

n(e) – the average number of planets per planetary system capable of supporting life.

f(l) – the fraction of planets that can support life where life actually begins.

f(i) – the fraction of planets with life were intelligence evolves.

f(c) – the fraction of planets with intelligence that develop long distance communications (such as radio).

L – The average number of years that civilizations continue to communicate (remain radio bright).

Find the value of each variable, multiply then all together and you end up with the number of intelligent civilizations that are currently capable of communicating with us. As simple as that! As you can see, Drake wasn’t as interested in simply the number of intelligent species; he wanted to know how many we could actually contact or at least listen in on. There could be many intelligent species out there that never develop technology for communications or decide for whatever reason that they don’t want to advertise their presence. If we can’t detect them, we can’t chat with them. Here, we will use the working definition of intelligence as a civilization that has the technology capable of interstellar communications.

We currently only know even rough values for the first two variables, R* and f(p).
R* is about 10 stars/year
f(p) is somewhere around 0.3 to 0.6
After these first two variables, anyone’s guess as about as good as any other. Just for fun, let’s have a go at it and see what we come up with:
R* = 10
f(p) = 0.5 (between the current estimates)
n(e) = 1 (Not all stars are likely to have planets that are favorable for life but some could have several. In our own solar system, there are several possible candidates. So, this number is likely fairly large. Let’s just call it one.)
f(l) = 1 (My guess is that given enough time and given a proper environment, life is likely to spring into existence. Again for simplicity, call it one.)
f(i) = 0.01 (Hmmm. I’m not so sure about this one. Just because you have life, doesn’t necessarily mean you get intelligence. Let’s go with a WAG [Wild-Ass Guess] of one in a hundred?)
f(c) = 0.01 (This is another factor that I’m really unsure of. I can imagine many reasons why a civilization comprised of intelligent creatures might never develop the technologies that we have or might make a conscious decision not to let their presence be known. Again, maybe one in a hundred??)

This leaves us with the variable L, the lifetime of a communicating civilization. This is the factor that truly matters. If we take humanity here on Earth to be an average example, we’ve had radio for roughly the last century. In that time, we’ve come perilously close to annihilating ourselves on several fronts; nuclear, environmental, wars and epidemics to name just a few. It seems that a technology that is at a level capable of broadcasting over interstellar distances is also capable of destroying itself! This argues that the lifetime of such a technology is often fleetingly short. On the other hand, perhaps some civilizations are wiser than us and are able to manage the dangers inherent in their technologies. One might imagine that such a civilization could have a vastly long lifetime. So, what’s the average life? I truly wish I knew.

In our example solution to the Drake Equation, so far we have:

N = 10 x 1 x 1 x 0.5 x 0.001 x 0.001 x L

N = 0.0005 x L

To get N, the number of communicating civilizations in our galaxy, up to just one, the average lifetime of such civilizations needs to be at least 2000 years! If it’s less than that, there aren’t likely to be many, if anybody, out there to talk to. Keep in mind that we’ve been at it for only about 100 years. On the other hand, if some civilizations can find ways to survive long-term, say millions of years, there could be hundreds to thousands of civilizations out there right now. So, what is the answer? We simply don’t know. Only through doing the searches to fill in the variables in Drake’s seminal equation can we hope to get to the answer.

Claude Plymate
Engineering Physicist
National Solar Observatory
Email: plymate@noao.edu