Mars wasn’t always the cold, dry world that it is today — billions of years ago it likely looked a lot more like Earth, with seas and rivers of liquid water on its surface and a thick atmosphere with air and clouds. But something happened over the course of Mars’ history to transform it from a warm, wet world to a cold, desiccated desert planet, and while there are many viable suggestions as to what process is responsible, no verdict has yet been delivered.
This video, just released by NASA’s Goddard Space Flight Center, shows what Mars might have looked like four billion years ago. As the camera tracks back the clouds gradually disappear, the lakes and rivers turn to rubble-strewn plains and the skies change from blue to pale orange. As we rise above the dust clouds that roll across the planet, we see the first evidence of modern times: NASA’s MAVEN spacecraft, flying high overhead to investigate the mystery of a lost Mars.
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Saturn might look like a placid beige ball in backyard telescopes but in reality it has very dynamic weather patterns and climates, rivaling the storms of Jupiter and the varied climates of Earth, based on long-term microwave observations by the Cassini spacecraft.
(Yes, microwaves are good for much more than heating up your coffee.)
Scientists working with data from NASA’s Cassini mission have confirmed the presence of a population of complex hydrocarbons in the upper atmosphere of Saturn’s largest moon, Titan, that later evolve into the components that give the moon a distinctive orange-brown haze. The presence of these complex, ringed hydrocarbons, known as polycyclic aromatic hydrocarbons (PAHs), explains the origin of the aerosol particles found in the lowest haze layer that blankets Titan’s surface. Scientists think these PAH compounds aggregate into larger particles as they drift downward.
“With the huge amount of methane in its atmosphere, Titan smog is like L.A. smog on steroids.”
– Scott Edgington, Cassini deputy project scientist
An incredible 1,200-mile-wide vortex of spiraling clouds swirling above Saturn’s north pole is seen in all its glory in this stunning image from NASA’s Cassini spacecraft, originally captured last year but recently released by NASA on April 29.
Taking advantage of a new orbital trajectory that puts it high above Saturn’s rings and poles, Cassini acquired the near-infrared images used to make this composite back on Nov. 27, 2012. The resulting image is false color — our eyes aren’t sensitive to those particular wavelengths of light — but still no less amazing!
Bored by blue? Saturn’s skies sure do have a lot more colors, as seen here in a color-somposite made from raw Cassini images acquired on Feb. 27, 2013.
With spring progressing on Saturn’s northern hemisphere (a season that takes 7 1/2 Earth years to pass!) the upper latitudes gradually receive more sunlight and thus more solar energy, warming the planet’s atmosphere and driving the upper-level winds and storms.
Although similar in size to Earth, the planet-next-door Venus is typically perceived as a hellish inferno of caustic clouds, crushing pressures and kiln-like temperatures. And while those are indeed all very much the case, Venus has recently been found to have a cooler side too… although it’s 125 km (77 miles) up in its atmosphere.
The pumpkin-orange colors of Titan’s thick clouds appear in stark contrast in front of the limb of Saturn, which appears quite blue along its sunlit limb due to Rayleigh scattering, the same process that makes the sky look blue here on Earth.
The image here is a color composite made from three separate raw images acquired by Cassini on July 1, 2012. Captured in red, green and blue visible light wavelengths, when combined the result is a more-or-less true color image as our eyes might see it. The final image was rotated to make the angle of sunlight come in from the left horizontally, and I teased out some detail in Saturn’s atmosphere.
Cassini was over 1.7 million miles from Titan when the images were captured.
Credit: NASA/JPL/SSI. Edited by J. Major.
On a related note, today another Saturn/Titan color composite I assembled in May was chosen for the popular Astronomy Picture of the Day page, or APOD as it’s known. Check it out here. The image first appeared on Universe Today on May 11, and was thereafter picked up by ESA and from there made its way to APOD. Very cool!