Date: December 19, 2011
Title: The Goldilocks Zone
Podcasters: Scotty J. and Destinee E.
Organization: Walden School of Liberal Arts
Link: For more information on the Astrobiology class at Walden School and projects we are working on, visit our blog at: elementsunearthed.com.
Description: Now that we are beginning to find exoplanets inside the habitable zone of their stars, the next step will be to look for signs of life on those planets. In this podcast, we discuss what the Goldilocks Zone of a star is – an area that is not too hot or too cold, where liquid water could exist. We look at the possibilities for life in our own solar system and how life-bearing planets and moons might be found even outside the zone.
Bio: Walden School of Liberal Arts is a K-12 charter school in Provo, Utah. The astrobiology class is new this year. Taught by David V. Black, the course focuses on the definition of life, the ingredients that are necessary for life to begin, where those ingredients may be found in our solar system, our quest to find habitable worlds orbiting nearby stars, and the search for extra-terrestrial intelligence. In addition to researching and recording these podcasts, the astrobiology students are also working with students in our 3D animation class to create a series of animations on the origin, evolution, and selenography of Earth’s moon for the Center for Lunar Origin and Evolution in Boulder, CO.
David Black has taught astronomy, chemistry, and multimedia courses at the high school level for over 20 years. He has been a NASA/JPL Solar System Educator and an Educator Facilitator for the NASA Explorer Schools program at JPL. This year, he won third place nationally in the Mars Education Challenge sponsored by Explore Mars, Inc. and the National Science Teacher Association. He is a frequent presenter at state and national science and technology teacher conferences. To contact David Black with questions about our projects, please e-mail him at: elementsunearthed@gmail.com.
Sponsors: This episode of “365 Days of Astronomy” is brought to you by NO ONE. Please consider sponsoring a day or two so we can continue to bring you daily “infotainment” into the new year.
Happy Holidays!
Transcript:
The Goldilocks Zone
Scotty:
Hello and welcome to the 365 Days of Astronomy. We are Scotty, Destinee, and Stephanie from Walden School of Liberal Arts in Provo, Utah.
Today we are going to learn about the Goldilocks Zone. So what is the Goldilocks Zone? It is a small area around a sun that isn’t “too hot” or “too cold” but just right for life. Astrobiologists disagree on what exact factors are needed for something to be considered alive, but they do agree on three conditions that must exist: life would need a liquid, such as water, for reactions to take place, a source of organic molecules, since carbon is the most likely element to base life on, and an energy source strong enough to support life functions, whether that is sunlight, volcanic heat, or some other form of energy.
Earth is in the center of the Goldilocks Zone around our sun. Sunlight provides enough energy for photosynthesis over most of the Earth’s surface, water is usually found as a liquid on Earth, and there are definitely organic molecules all over the place. Mars is just barely inside the outer edge of the zone and Venus is just barely outside the inner edge of it. So it might be possible for Mars to have life on it. Mars has ice under its soil but its atmosphere is now too thin for liquid water to exist on the surface, but it could exist in solutions below the surface.
Destinee:
Before the Voyager probes in the late 1970s and 1980s, scientists thought only two planets were in the habitable zone: Mars and Earth, and that these planets were the only ones which could contain life.
But as they have looked outside the Goldilocks Zone they have found that maybe there is life on some of the moons of other planets, such as Jupiter and Saturn, and maybe life can exist in places no one had considered before.
Europa is a moon of Jupiter that has a crust of ice over a layer of salty water that may be as much as 60 miles deep, which means that Europa has more liquid water on it than all of Earth. Much of this liquid water came from comets that collided with this moon and from volatiles left over from the formation of the solar system. If comets brought all the water, then they also brought organic molecules. Maybe this ocean can contain some living things.
The Galileo probe, which orbited Jupiter, found that Europa’s surface is smooth, with cracks and blocks that look very much like ice flows in Earth’s Arctic Ocean.
They have only seen three craters, which means it has a very young, actvie surface, something like Earth. The atmosphere on Europa has a little bit of oxygen, but it’s not produced biologically. The atmosphere is maintained by particles that hit the cold surface and produce water vapor, then the water vapor turns into oxygen and hydrogen, then the hydrogen leaves the atmosphere with the oxygen remaining behind.
Testing the magnetic field of Europa shows that it must have a thick layer of salty water to produce the magnetic fields seen. The most likely reason why water is a liquid on Europa, even though it is outside the Goldilocks Zone of the sun, is that Europa is pulled and stretched in a gravitational tug-of-war between Jupiter and the outer moons Ganymede and Callisto. As its crust is flexed, Europa heats up inside and probably has active volcanoes erupting under the liquid water, just as Earth has volcanic vents at the mid-ocean ridges. So Europa has all three of the ingredients necessary for life.
We have plans on the drawing board to send an orbiter to Europa to map out where the ice crust is thinnest. We’ll land a probe at that spot and send a nuclear-powered torpedo down into the ice, melting the ice as it goes. Once it reaches liquid water it will swim around like a submarine and look for evidence of life. It will transmit a video feed and scientific data up through a wire tether to the lander and from there back to Earth. It will be a difficult and expensive mission, but it may be the only way to answer the question of whether or not Europa has life.
Other places that may have the ingredients for life are Saturn’s moons Titan and Enceladus. Titan has been a great mystery until recently. The Huygens probe parachuted down through the thick methane atmosphere and landed on the surface. It sent back photos on its way down, showing something very surprising: There were lakes, river valleys, and eroded mountains on Titan that looked very much like the landscape of Earth. Except Titan is so cold that the mountains are made of ice and the lakes are liquid methane and propane. So there is a liquid and obviously organics, but is Titan warm enough for life to get going?
Recently the Cassini probe found that Enceladus has a smooth surface, even smoother and brighter than Europa. It also has a series of cracks near the south pole that are radiating heat and are spewing out a fountain of liquid water into space, which freezes back into the snow that coats the surface. Since there seems to be liquid water below the ice and snow, and a heat source similar to Europa, and probably organics as well, it is now another candidate for life in our solar system.
To try and understand how life might get started and survive under such difficult conditions, astrobiologists travel the Earth looking for extreme environments that are hot and dry or cold and dry, in glacier ice, under two miles of rocks in deep gold mines in Africa, or in caves sealed off from the light. Everywhere they go, they find life. It seems that once life gets started, it is very hard to wipe out. Scientists think since we find living things in the most extreme places on Earth then maybe there could be life on other planets. This is especially true if the Goldilocks Zone is bigger than we thought.
Scotty:
So far we can only search in our solar system, but as technology grows, we will be able to travel farther.
What is the possibility of finding life elsewhere in this universe? We are discovering new exoplanets orbiting nearby stars. As our techniques become more refined, we are now beginning to find Earth-sized planets inside the habitable zone of their stars. Even gas giant planets in the zone might have livable moons. Given the possibilities in our own solar system, the chances are good to find life elsewhere.
There are probably millions of planets and moons in the Milky Way and 100 billion galaxies in the universe. The possibility of just one of these millions of trillions of planets and moons being habitable is huge, and it gets even huger with new knowledge of multiple universes. Scientists think that our universe might not be the only one out there.
One proposed mission, the Terrestrial Planet Finder, would fly a formation of interferometers near Jupiter’s orbit. They would be able to blank out the glare of a star and then photograph the planets orbiting it. Even a small photo would show if there’s liquid water, clouds, and oxygen or ozone. We could detect chlorophyll and conclude the planet probably has life. The remaining question is whether or not we could ever travel to those distant planets and “ground truth” our observations.
Maybe some day one of you listening to this podcast will be able to figure out a way.
Thank you for listening to the 365 Day of Astronomy. Hope to see you soon.
End of podcast:
365 Days of Astronomy
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