Titan's Smoggy Sunsets Help Scientists Devise Tools to Find Evidence of Life Elsewhere
Using data collected by Cassini's Visual and Infrared Mapping Spectrometer, or VIMS, while observing Titan's sunsets, researchers created simulated spectra of Titan as if it were a planet transiting across the face of a distant star. The research helps scientists to better understand observations of exoplanets with hazy atmospheres. Courtesy NASA/Cassini Mission
As many a person relaxing at the end of a long day can tell you, there's a lot you can learn by watching a sunset. Hazy skies sometimes produce gorgeous colorful sunsets here on Earth (due to particles of dust and smoke in the air scattering various colors of light), for example. That's one example of an atmosphere acting like a "prism". But, atmospheres do more than scatter light. They also absorb light that passes through from distant objects (such as stars), which allows some wavelengths to pass through. If you look at the light of star passing through a planetary atmosphere with an instrument called a spectrograph), you will see "dropouts" in the spectrum (the graph of light) the instrument produces. Those dropouts indicate that something in the atmosphere absorbed certain wavelengths of light. That "something" could be a gas such as oxygen or methane or carbon dioxide. And, that means the gas exists in the atmosphere. In the case of distant worlds around other stars (called exoplanets), being able to measure chemicals in an atmosphere is a big step toward searching out the possible existence of life on those worlds.
So, how does this help astronomers find life elsewhere? And, what does Saturn's smoggy moon Titan have to do with it?
Our Sun Just LOOKS Friendly
What if we could determine if a given star is likely to host a planetary system like our own by breaking down its light into a single high-resolution spectrum and analyzing it? A spectrum taken of the Sun is shown above. The dark bands result from specific chemical elements in the star's outer layer, like hydrogen or iron, absorbing specific frequencies of light. By carefully measuring the width of each dark band, astronomers can determine just how much hydrogen, iron, calcium and other elements are present in a distant star. The new model suggests that a G-class star with levels of refractory elements like aluminum, silicon and iron significantly higher than those in the Sun may not have any Earth-like planets because it has swallowed them. (N.A.Sharp, NOAO/NSO/Kitt Peak FTS/AURA/NSF)
It looks like Earth may have dodged a ravenous Sun, early in its history! A graduate student at Vanderbilt University has developed a model of stellar formation that shows the effect of a "hungry" Sun-like star on the materials in its birth cloud. If it eats a lot of the rocky material from which Earth-like planets (terrestrial planets) form, then there's a good chance those worlds won't form at all.
Trey Mack's model estimates the effect that such a diet has on a star's chemical composition and has used it to analyze a pair of twin stars that both have their own planets.
What does this mean? Let's look at stars in general and what they're made of.
Digging Deep to Learn More about Mars
NASA/JPL announced this week that it is starting the build the next generation of Mars lander, nicknamed InSight. It will head to the Red Planet on 2016, and spend its time using seismic sensors and other instruments to give planetary scientists a good idea of the interior of Mars. Let's take a look at just how the InSight mission will do its job.
Behemoth Collisions Spur Starbirth
A frame from the simulation of the two colliding 'Antennae' galaxies. Here the galaxies are re-shaped after their first encounter. High resolution allows the astrophysicists to explore the smallest details. Stars are formed in the densest regions (yellow and red) under the effect of compressive turbulence. Star formation is more efficient here than in normal galaxies like our Milky Way. Credit: F. Renaud / CEA-Sap
The history of the universe is filled with tales of galaxy collisions. The first galaxies formed when proto-galaxies (shreds of galaxies) collided, mingling stars and gas. As time went by, these collisions resulted in the large stellar cities we see today. Our Milky Way Galaxy formed through numerous collisions and is still 'ingesting' other galaxies today, such as the Sagittarius Dwarf spheroidal galaxy. Astronomers have found its stars streaming into the Milky Way.
Seeing a Distant World from Earth
Beta Pictoris b (the small white dot to the lower right of its star (Beta Pictoris) is a giant planet - several times larger than Jupiter, and is approximately ten million years old. These near-infrared images (1.5-1.8 microns) show the planet glowing in infrared light from the heat released in its formation. The bright star Beta Pictoris is hidden behind a mask in the center of the image.
Image credit: Processing by Christian Marois, NRC Canada.
This may look like a piece of abstract art, but it's really one of the finest images of an extrasolar planet ever taken from Earth. The Gemini Planet Imager was able to capture this view of a world circling the star Beta Pictoris. The name of the planet (for now) is Beta Pictoris b, and it lies nearly 64 light-years from Earth.
Its Great Red Spot is Getting Smaller!
The planet Jupiter is a world of superlatives. It is the largest gas giant in the solar system, it is the most massive planet in our neighborhood, it probably has the most moons, its largest moons exhibit ice and rock volcanism, it has a thin ring of dust around it, it may have a rocky core about the size of Earth, its atmosphere is incredibly huge and thick, and it has one of the largest storms of any planet: the Great Red Spot.
Look Up! See Stars and More!
Astronomy is one of the easiest sciences to learn about. People have been "doing" astronomy since the first stargazers stepped out under a starry sky and looked up. The astronomer Carl Sagan used to say that we are the descendants of stargazers. If our ancestors hadn't looked up and learned to use the sky, the survival of early people and societies would have been much more difficult. It's good for us that the first stargazers learned to use the sky to learn the seasons, and use that knowledge to determine hunting seasons and planting times. Because of their knowledge of the stars, they ate better and birthed more stargazers. ...
Researchers Look at Humanity's Readiness for First Contact
Aliens! Humans have been searching for some evidence of life outside Earth for many years. The serious scientific approach has been the business of a group called SETI: the Search for Extra-terrestrial Intelligence. These scientists include astrobiology researchers, astronomers, planetary scientists, and even a large group of public supporters who help them sift through radio astronomy data to look for signals from "out there".
SETI scientists want to send messages to the cosmos, hoping that somewhere, somehow, someone will "pick up the phone" and listen.
Are we ready for the answer? What will happen when that does happen? Will humans react in panic and fear, or will we look forward to the new contact? A lot depends on where our cultural expectations lie. To be fair, nobody really quite knows HOW anyone SHOULD react, despite all the science fiction movies and books that explore the possibilities.
At least one researcher is looking at the ethical and sociological implications of sending messages to unknown "neighbors" in space. Neuro-psychologist Gabriel G. de la Torre, professor at the University of Cádiz wonders about this quite a bit. He asks, "Can such a decision be taken on behalf of the whole planet? What would happen if it was successful and 'someone' received our signal? Are we prepared for this type of contact?"
Jupiter's Moon May have Layers
This artist's concept of Jupiter's moon Ganymede, the largest moon in the solar system, illustrates the "club sandwich" model of its interior oceans. Courtesy NASA/JPL-Caltech
There's something different about Ganymede, the icy moon orbiting the planet Jupiter (which actually has four large moons visible to us through binoculars or a telescope). It's not just that it has an icy crust overlaying an ocean of salty water. Or that its surface seems to be mottled, cracked, and cratered, indicating interesting events happening both above and below its crust.
No, it's more that Ganymede may actually have several layers of oceans interspersed between layers of ice, with a rocky core at the center. If that's true, then planetary scientists think it's entirely possible this moon (the largest one in the solar system), could harbor primitive life. There's no way to know for sure if it DOES have life. That would take a specialized mission to get to Ganymede and dive under its frozen crust. Such missions have been discussed, but there's nothing ready to go just yet.
Exploring the Intergalactic Medium
A Cosmic Web Imager view of a distant quasar. The blue denotes hydrogen gas surrounding and flowing into the quasar in the early universe.
It may seem like an easy question to answer: what is there out between the galaxies? The answer is NOT "an empty vacuum", thanks to a series of images taken with a specialized instrument called the Cosmic Web Imager built by the California Institute of Technology (CalTech). It is being used at Palomar Observatory on the 200-inch Hale telescope to look between galaxies and measure the thin mix of gases that astronomers now know exists there. They call it "dim matter" because it isn't bright like stars or nebulae, but it's not so dark it can't be detected. The Cosmic Web Imager looks for this matter in the intergalactic medium (IGM) and finds it. How does it do this?