Venus’ Variable Evolution


For every backyard astronomer, we know 4.5 billion years ago, both Venus and Earth were formed with nearly the same radius, mass, density and chemical composition. Venus is like Earth’s evil twin, but why is the climate on both worlds so widely varied? Scientists analysing the data from the orbiting European Venus Express spacecraft are finally putting the pieces of the geological and climatological puzzle together as they take a closer look at Venusian evolution.

Today, Professor Fred Taylor of Oxford University presented the scenario in a talk at the Royal Astronomical Society National Astronomy Meeting in Belfast. According to the studies, Venus appeared to have evolved very rapidly compared to the Earth during the early formation of the solar system. Thanks to data obtained from the Venus Express, it would appear our wicked sister planet once had significant volume of water covering the surface… Oceans which were lost in a very short geological timescale. As the water disappeared, the geological evolution of the surface of Venus slowed quickly – unable to develop plate tectonics like the Earth. Biological evolution could never happen. If, at one time, Venus mirrored Earth in climate and habitability terms, then it evolved too quickly at first, then too slowly.

Venusian atmosphere stripped away by solar winds - ESA‘They may have started out looking very much the same,’ said Professor Taylor, ‘but increasingly we have evidence that Venus lost most of its water and Earth lost most of its atmospheric carbon dioxide.’

Here on Earth, carbon dioxide is captive plant life, minerals and the crust itself. Not to harp on global warming, but the release CO2 back into the atmosphere is a source of climatic change. On Venus, the majority of the carbon dioxide resides it its atmosphere, leaving the surface temperature at a searing 450 degrees Celsius. This slows or stops geological as well as biological evolution.

‘The interesting thing is that the physics is the same in both cases’ said Prof Taylor. ‘The great achievement of Venus Express is that it is putting the climatic behaviour of both planets into a common framework of understanding.’

But, we haven’t heard the last from Venus Express just yet. Due to operate until May 2009, scientists involved in the project are already busy applying for an extension until 2011.

‘We have plans for joint operations with the Japanese spacecraft called Venus Climate Orbiter that will arrive in December 2010’, said Taylor. ‘Together, we can do things neither could do alone to crack some of the remaining puzzles about Venus.’

Organic Molecules Found Outside our Solar System


Organic molecules are thought by scientists to be instrumental in kickstarting life as we know it on Earth. Within our Solar System they can be found in comets, and they cause the redness of the clouds of Saturn’s moon Titan. New observations of a planet-forming disk around a star 220 light-years from Earth reveal for the first time that these molecules exist elsewhere in the Universe.

Astronomers at the Carnegie Institute have detected the presence of organic molecules in the dusty disk surrounding HR 4796A, an eight-million year-old star in the constellation Centaurus. Using Hubble’s Near-Infrared Multi-Object Spectrometer they analyzed the light coming from the disk and found that its red color is due to large organic carbon molecules called tholins. The analysis ruled out other causes of the red light, such as iron oxide.

“Until recently it’s been hard to know what makes up the dust in a disk from scattered light, so to find tholins this way represents a great leap in our understanding,â€? said John Debes of the Carnegie Institute’s Department of Terrestrial Magnetism, one of the authors of the study.

Just as in our early Solar System, the disk of dust is in the process of forming planets. The collision of small bodies like asteroids and comets creates the dust in the disk, and the organic molecules present on these objects could then be scattered on any planets orbiting the star. This discovery makes it clear that it is possible for organic molecules to exist in the early stages of planet formation, paving the way for the possible development of life later on.

Organic molecules are thought to be essential to the development biological organisms because they are made up of carbon, the building block of life on Earth. The discovery of these molecules elsewhere in the Universe does not mean that life exists there yet – or even that it will in the future – but it does increase the tantalizing prospect of life forming outside our Solar System.

The study was published in the current Astrophysical Journal Letters by John Debes and Alycia Weinberger of the Carnegie Institution’s Department of Terrestrial Magnetism with Glenn Schneider of the University of Arizona.

Source: Carnegie Institute Press Release

Meteorites Reveal Mars’ Past: Molten Surface, Thick Atmosphere


If Mars ever had water flowing on its surface, as the many canyons and riverbed-like features on the Red Planet seem to indicate, it also would have needed a thicker atmosphere than what encircles that planet today. New research has revealed that Mars did indeed have a thick atmosphere for about 100 million years after the planet was formed. But the only thing flowing on Mars’ surface at that time was an ocean of molten rock.

A study of Martian meteorites found on Earth shows that Mars had a magma ocean for millions of years, which is surprisingly long, according to Qing-Zhu Yin, assistant professor of geology at the University of California- Davis. For such a persistent event, a thick atmosphere had to blanket Mars to allow the planet to cool slowly.

Meteorites called shergottites were studied to document volcanic activities on Mars between 470 million and 165 million years ago. These rocks were later thrown out of Mars’ gravity field by asteroid impacts and delivered to Earth — a free “sample return mission” as the scientists called it — accomplished by nature.

By precisely measuring the ratios of different isotopes of neodymium and samarium, the researchers could measure the age of the meteorites, and then use them to work out what the crust of Mars was like billions of years before that. Previous estimates for how long the surface remained molten ranged from thousands of years to several hundred million years.

The research was conducted by the Lunar and Planetary Institute, UC Davis and the Johnson Space Center.

Planets form by dust and rocks coming together to form planetisimals, and then these small planets collide together to form larger planets. The giant collisions in this final phase would release huge amounts of energy with nowhere to go except back into the new planet. The rock would turn to molten magma and heavy metals would sink to the core of the planet, releasing additional energy. The molten mantle eventually cools to form a solid crust on the surface.

Although Mars appears to no longer be volcanically active, NASA’s Mars Global Surveyor Spacecraft discovered that the Red Planet hasn’t completely cooled since its formation 4.5 billion years ago. Data from MGS in 2003 indicated that Mars’ core is made either of entirely liquid iron, or it has a solid iron center surrounded by molten iron.

Original News Source: UC Davis Press Release

Earthlike Planet Forming Around a Distant Star


Astronomers believe the Earth formed out of a ring of gas and dust surrounding the Sun. Over the course of several million years, dust particles stuck together, and then collided with larger and larger chunks until all the material in the ring formed up into a single planet. The heavier elements separated from the lighter elements, and sunk down into the centre of the Earth. And if astronomers are right, it’s happening all over again, in a star system 424 light-years away; another Earth is under construction.

The discovery was announced today by physicists from the Applied Physics Laboratory at Johns Hopkins University. Using data gathered by NASA’s Spitzer Space Telescope, the researchers have uncovered a dust belt around a star called HD 113766. And if the theories of planetary formation are correct, this dust belt will eventually turn into a planet with roughly the mass of the Earth.

To make things even more interesting, this dust belt is located in the star’s habitable zone, where liquid water could exist on any rocky planet that forms in the region.

And the timing is right too. Here’s one of the researchers, Dr. Carey Lisse, “If the system was too young, its planet-forming disk would be full of gas, and it would be making gas-giant planets like Jupiter instead. If the system was too old, then dust aggregation or clumping would have already occurred and all the system’s rocky planets would have already formed.”

The astronomers can even tell how “processed” this material is. If it were totally unprocessed, it would be like the comets, icy remnants largely unchanged since the early Solar System. And if it was heavily processed, it would be like the asteroids, where the heavy elements have almost completely separated from the lighter elements. Instead, it’s all mixed up.

The rocky planets haven’t formed yet.

The paper will be published in an upcoming edition of the Astrophysical Journal.

Original Source: APL News Release

Gas Giants Gobbled Up Most of Their Moons

Even though our Solar System’s gas giants vary widely in size and mass, they do have something in common. Each planet is roughly 10,000 times more massive than the combined mass of all their moons. During planetary formation, rocky moons grew out of the solid material surrounding each planet. As these moons grew larger, leftover gas slowed them down, and they fell into the planet to be consumed. The moons we see today were the last ones to form around their parent planets, after the gas had dissipated.
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