Earth: The Lone Pale Blue Dot?

[Waspie_Dwarf]

Earth: The Lone Pale Blue Dot?

A recent photo from the Cassini spacecraft shows the mighty planet Saturn, and if you look very closely between its wing-like rings, a faint pinprick of light. That tiny dot is Earth bustling with life as we know it. The image is the second ever taken of our world from deep space. The first, captured by the Voyager spacecraft in 1990, stunned many people, including the famous astronomer Carl Sagan who called our seemingly miniscule planet a "pale blue dot" and "the only home we've ever known."


Image above: Earth, seen as a pale blue dot from Saturn.
Image credit: NASA/JPL/Space Science Institute
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+ High resolution JPEG (97Kb)

Last September, a portion of Cassini's picture showing Earth was unveiled to an auditorium full of scientists attending the third Pale Blue Dot workshop at the Adler Planetarium in Chicago. The workshop brought together scientists from across the country and beyond to talk about how to find life elsewhere in our universe, a central theme in the interdisciplinary field of astrobiology. When the workshop participants were presented with the picture, they spontaneously began to clap. One of their fundamental goals is to capture a portrait like Cassini's showing another "pale blue dot" like Earth in a planetary system beyond our own.

If scientists do ever acquire such a photo, how will they figure out whether anybody is home? Workshop participant Dr. Wes Traub of NASA's Jet Propulsion Laboratory in Pasadena says a photo of a light-blue extrasolar planet - a planet outside our solar system - might indicate the planet has an atmosphere, a tantalizing sign that it could support life. "In our solar system, we are the only small light-blue planet," he said. Earth appears blue because its atmosphere scatters blue light around, literally filling the sky with the color blue.

But colors are only clues. A planet with an atmosphere might be blue, or not. Mars has an atmosphere, albeit a thin one, and it's red. The blue light in the martian skies is soaked up by iron-containing molecules on the surface that radiate red.

Ultimately, astrobiologists will need additional data to determine whether an extrasolar planet is habitable, and if so, whether it harbors life. Future planet-finding missions like NASA's Terrestrial Planet Finder are expected to return both valuable "spectral" data and imagery of planets looking small enough to fit on a pin. Spectra are surveys of an object's rainbow-like array of different wavelengths of light. They reveal the presence of specific molecules.

To determine if a planet is livable, scientists will look for carbon dioxide and water vapor, signposts that a planet has an atmosphere and oceans, respectively. Atmospheres not only provide air to breathe, but also act like blankets to keep a planet warm and help buffer potential residents from damaging ultraviolet and cosmic rays. Oceans help regulate a planet's temperature and provide liquid water, an essential ingredient for life on Earth.

Other molecules enveloping a planet, such as oxygen, ozone and methane, can suggest that life itself has taken root. On Earth, oxygen is "breathed out" by plants, and methane by micro-creatures living in swamps and animals. These chemicals don't stick around for long on their own, so if they are hanging around an extrasolar planet, then something must be pumping the stuff out. That something could be life, but this isn't always the case. Saturn's moon's Titan is shrouded in an atmosphere containing lots of methane not produced by life.

Scientists say that oxygen is a more reliable sign of life than methane, but if they found large quantities of both, they'd be more convinced. "Finding two of these molecules together would be much better than one. The more, the better," said Dr. Victoria Meadows of NASA's Spitzer Science Center, Pasadena, who served as chair of the third Pale Blue Dot conference. "For example, if we found carbon dioxide, oxygen and water vapor, in addition to methane, then we'd be pretty convinced that we were looking at an environment like our own."


Image above: A view of Earth from
Voyager 1, at a distance of more than 4
billion miles. Earth is the dot in the middle
of the bright streak.
Image credit: NASA/JPL
+ Full image and caption
+ Browse version of image

Not all molecules are a good sign. For example, abundant amounts of sulfur dioxide suggest a dead, dry planet. This chemical would dissolve into a planet's ocean if it had one, so its presence means it is unlikely there's much water around. Venus is one such parched planet, with a thick atmosphere containing sulfur and carbon dioxide.

There are still other signs of life that astrobiologists will seek out. At the workshop, scientists talked about looking for pigments from planets coated in slime, as the young Earth might have been, and the systematic search for technological signs of civilizations. They discussed observing global changes in a planet over time - a mark of weather, continents and possibly life. And they talked about the colors of vegetation, especially the infrared light that plants shine in brilliantly.

When it comes to exotic planets, scientists say that we should be prepared for the unexpected. "One of the messages to come out of the workshop is that planets are a complicated result of what they are made of, and their histories. Planets are potentially as diverse as people," said Meadows. "In only the last few years, we've found evidence that extrasolar planets may not be anything like those in our solar system. That's what's so exciting. Not just the possibility of finding another planet like the Earth, but the chance to also look for truly alien worlds."

Media contact: Whitney Clavin (818) 354-4673/JPL

Source: NASA - Exploring the Universe

[frogfish]

Beautiful picture!

Makes us feel so little.

Edited November 5, 2006 by frogfish

[Homerduff]

indeed, that's why people who say that there isn't any ET life are plain stupid..

[Waspie_Dwarf]

indeed, that's why people who say that there isn't any ET life are plain stupid..

Why are they stupid? Until there is proof of extraterrestrial life it is as equally a valid point as saying there must be extraterrestrial life? The fact of the matter is we have no real evidence either way, hence it is just as stupid to say ETs MUST exist.

Edited November 5, 2006 by Waspie_Dwarf

[Leonardo]

Fantastic image.

I would love to go into space. To see the Earth from a great distance as some astronauts have must give you a feeling at once both profound and very humbling.

[Waspie_Dwarf]

Fantastic image.

I would love to go into space. To see the Earth from a great distance as some astronauts have must give you a feeling at once both profound and very humbling.

Agreed.

I wonder how the first astronauts to go to Mars will feel as their home planet diminishes to no more than a bright point of light in the sky?

[Leonardo]

Agreed.

I wonder how the first astronauts to go to Mars will feel as their home planet diminishes to no more than a bright point of light in the sky?

If I'm on the bus I'll let you know

[shun]

When I looked at the image, I noticed plumes and specks of light color. I knew the plumes were moon related, and assumed the specks were, as well. Finally, I determined the moons were not visible using the wavelengths presented in the image (UV, NIR), nor at that resolution. The alternative is the specks are fuzzy stars, except for the pixels that represent Earth.

Then, I found the Cassini science illustrator tried to enhance the plumes in an image of similar contrast, and also discussed the different degrees of color in the rings.

Essentially, the plumes are from possible geysers on Enceladus; and, as part of the E-Ring, they travel at a different speed than the moon.

The variations in color depth throughout the rings has to do with the angle of the shot (15 degrees above the rings), and the sizes and composition of the particles.

Edited November 6, 2006 by shun

[shun]

This illustration with the moons was on a JPL webpage, but the names were illegible. Essentially, the outer moons are beyond the ring system, and Enceladus is embeddded in the diffuse outer ring, known as the E-Ring. The plumes emanate from there, of course, but we can not see Enceladus in the article's image.

Also, here is second illustration regarding the rings.

(I noticed all my images were deleted, somehow, so I re-attached them)

Edited November 6, 2006 by shun

[Picturesque Orion]

Why are they stupid? Until there is proof of extraterrestrial life it is as equally a valid point as saying there must be extraterrestrial life? The fact of the matter is we have no real evidence either way, hence it is just as stupid to say ETs MUST exist.

Waspie dwarf why do we always need proof of everything? Of caurse there must be extraterrestial life. You can see it right now, our earth is so small amd the universe is so big, you really think that, that is the only pale blue dot with life in space. There are billions of galaxies in the universe found, yet to be explored, and find billions more, so I think that concept is proof already. They don't need us to show us it is there we just know it by simple logic. Scientists already proofed that bacteria can survive in space for a determined time so I really don't understand why we need so much proof. I am sure there is life out there even if they are small bacteria but they are alive. Maybe finding another civilization is dificult but it can also be found because this universe that we live in is full of billions of galaxies whith billions of stars and whith trillions of planets( the galaxies of caurse ). So the odds here are very high. Maybe water is not the only substance that life need to exist. So thats why I think that people who don't believe that life is somewhere out there in the universe are simply not think well because we as human beings only have to use our logic to elaborate that topic. Hey, maybe there is no other life in the milky way but there are billions or trillions of other galaxies wich can sostain some kind of life even if it is microscopic. Hey, all of us know how big a galaxy can be.

Cheers

Ghostkol.

[Waspie_Dwarf]

There are billions of galaxies in the universe found, yet to be explored, and find billions more, so I think that concept is proof already

Waspie dwarf why do we always need proof of everything? Of caurse there must be extraterrestial life.

Because with out evidence the statement, "the Earth is unique and life can only exist here" is equally valid, as is "God only made one habitable planet".

Of caurse there must be extraterrestial life.

The statement "of course there must be life" is simply wrong. There is no "of course" about it. Without evidence we can try to calculate the odds all we like but we just don't know the answer.

There are billions of galaxies in the universe found, yet to be explored, and find billions more, so I think that concept is proof already.

No, all this proves is that the universe is very big.

this universe that we live in is full of billions of galaxies whith billions of stars and whith trillions of planets( the galaxies of caurse ). So the odds here are very high.

Just because something has a high statistical probability of occurring it does not follow that it MUST occur.

I say this despite the fact that I am a firm believer that extraterrestrial life exists, but I recognise that with out evidence that's all it is, a belief.

Anyway this is all getting rather off topic, there are many threads on this subject elsewhere on the site.

[Picturesque Orion]

Because with out evidence the statement, "the Earth is unique and life can only exist here" is equally valid, as is "God only made one habitable planet".

The statement "of course there must be life" is simply wrong. There is no "of course" about it. Without evidence we can try to calculate the odds all we like but we just don't know the answer.

No, all this proves is that the universe is very big.

Just because something has a high statistical probability of occurring it does not follow that it MUST occur.

I say this despite the fact that I am a firm believer that extraterrestrial life exists, but I recognise that with out evidence that's all it is, a belief.

Anyway this is all getting rather off topic, there are many threads on this subject elsewhere on the site.

You are right Waspie anyways good picture though.