Saturn’s Mysterious Moons

Launched three years before the new century… a spacecraft wound its way through the empty reaches of the solar system. On Earth, its progress was little noted, as it swung twice by the planet Venus, then our moon. And Earth. The asteroid belt. And Jupiter.

Almost seven years later, on the first of July 2004, the Cassini probe entered the orbit of Saturn. It then began to compile what has become one of the greatest photographic collections of all time, of a giant gas planet, surrounded by colorful rings, guarded by a diverse collection of moons, and millions of tiny moonlets.

Within this record, is a trail of clues… pointing to the energy sources and complex chemistry needed to spawn life. What are these mysterious worlds telling us about the universe, and Earth?

In the outer reaches of the solar system, a billion and a half kilometers from the Sun… there is a little world known as Enceladus. Nearly all of the sunlight that strikes its icy surface is reflected back into space, making it one of the brightest objects in the solar system.

At its equator, the average temperature is minus 198 degrees Celsius. It can rise about 70 degrees higher Continue reading Saturn’s Mysterious Moons

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Solar Tsunami

The SOHO spacecraft has recorded the effect of all this rising energy. Its ultraviolet sensors show a wavy pattern of gas on the sun’s surface, along with the super-hot halo of gas called the corona.

The white regions are places where the rising gas suddenly escapes.

Immense loops of ionized gas, ten times the diameter of Earth, rise and fall back. These solar prominences are hot, about 60,000 degrees Celsius.

But there are times when the release of energy on the solar surface gets bottled up, by magnetic fields generated by the sun’s spinning turbulent core.

Using data from the sun’s exterior, scientists have modeled these fields as they erupt all around the sun’s surface, twisting and looping.

Heat rising toward the surface follows these magnetic field lines, which can also stifle the rising columns, forming relatively cool patches.

That’s where sunspots form. Four centuries ago, Galileo Galilei was the first to argue that these blotches were actually on the Sun’s surface, though he suspected they were clouds.

Their nature remained unclear until 1908, when the astronomer George Ellery Hale demonstrated the link between sunspots and intense magnetic fields.

Over the years, scientists have drawn their strange shapes in an effort to understand them.

What they Continue reading Solar Tsunami

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Where We Stand in the Cosmic Energy Continuum

Today, energy is very much on our minds, as we search for ways to power our civilization and serve the needs of our citizens.

But what is energy? Where does it come from? And where do we stand within the great power streams that shape time and space?

Energy comes from a Greek word for activity or working. In physics, it is simply the property or the state of anything in our universe that allows it to do work. Whether it is thermal, kinetic, electro-magnetic, chemical, or gravitational.

The 19th century German scientist Hermann von Helmholtz found that all forms of energy are equivalent, that one form can be transformed into any other. The laws of physics say that in a closed system – such as our universe – energy is conserved. It may be converted, concentrated, or dissipated, but it is never lost.

James Prescott Joule built an apparatus that demonstrated this principle. It had a weight that descended into water and caused a paddle to rotate. He showed that the gravitational energy lost by the weight is equivalent to heat gained by the water from friction with the paddle.

That led to one of several basic energy Continue reading Where We Stand in the Cosmic Energy Continuum

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Hubble Targeting the Big Questions

The NASA/ESA Hubble Space Telescope is working on three of the most ambitious projects in its history just now. These multicycle treasury programs are using Hubble’s unique ability to observe across the spectrum from ultraviolet, through visible, to infrared light, to build up a library of data which will serve astronomers for many years.

After circling the Earth for over two decades, Hubble has been responsible for many fascinating scientific discoveries. After the visit by astronauts in 2009 to service the spacecraft and to install new instruments, the telescope is now at the height of its powers.

As the observatory has matured, attention has turned to some ambitious projects on a scale that would not have even been considered a few years ago. Between them, these projects could help answer some of the biggest questions in astronomy today, and will contribute to science for many years to come.

Now, observing time on Hubble is a very precious commodity and it’s hugely sought after. That means that when astronomers want to use Hubble, they have to apply for observing time. And in their application, they have to be very detailed about what it is exactly they want to study, and how they’re going Continue reading Hubble Targeting the Big Questions

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Cosmic Journeys – Mars: Earth that Never Was

Did Mars long ago develop far enough for life to arise? If so, does anything still live within Mars’ dusty plains, beneath its ice caps, or somewhere underground?

In 1964 the Mariner Four spacecraft flew by Mars and got a good look. What it saw looked more like the Moon than the Earth. Then, in the mid-1970’s, two lander-orbiter robot teams, named Viking, went in for an even closer look. The landers tested the soil for the chemical residues of life. All the evidence from Viking told us: Mars is dead. And extremely harsh.

The mission recorded Martian surface temperatures from -17 degrees Celsius down to -107. We now know it can get even colder than that at the poles. The atmosphere is 95% carbon dioxide, with only traces of oxygen. And it’s extremely thin, with less than one percent the surface pressure of Earth’s atmosphere.

And it’s bone dry. In fact, the Sahara Desert is a rainforest compared to Mars, where water vapor is a trace gas in the atmosphere. On Earth, impact craters erode over time from wind and water… and even volcanic activity. On Mars, they can linger for billions of years.

Earth’s surface is shaped and reshaped by Continue reading Cosmic Journeys – Mars: Earth that Never Was

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Voyager Humanity’s Farthest Journey

From NASA JPL marking the passage of the twin Voyager spacecraft beyond our solar system. We knew we were on a journey of discovery when we launched the Voyager spacecraft, but we had no idea how much there was to discover.

We had a sense that we knew what it felt like to be Magellan or Columbus.

Time after time we were surprised by seeing things that we had not expected or even imagined. From volcanoes erupting from the moon Io to the possibility of a liquid water ocean under the icy crust of Europa. Titan, where we found an atmosphere. Uranus’ small moon Miranda, which had one of the most complex geologic surfaces we’d seen. Even at Neptune, Triton, 40 degrees above absolute zero, even there there were geysers erupting.

It’s the only spacecraft that’s gone by Uranus. It’s the only spacecraft that’s gone by Neptune. Everything we know about those planets we know from Voyager.

To see those first pictures coming in from the outer solar system, for the first time what had been a point of light in the sky was a place.

I really credit the people that designed the mission, both the engineers and the Continue reading Voyager Humanity’s Farthest Journey

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How an Asteroid Got a Rooster Tail

“The dust cloud around Scheila could be 10,000 times as massive as the one ejected from comet 9P/Tempel 1 during NASA’s UMD-led Deep Impact mission,” said co-author Michael Kelley, also at the University of Maryland. “Collisions allow us to peek inside comets and asteroids. Ejecta kicked up by Deep Impact contained lots of ice, and the absence of ice in Scheila’s interior shows that it’s entirely unlike comets.”

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Flare States of the Crab Nebula

From NASA Astrophysics and the amazings at Goddard Space Flight Center. The famous Crab Nebula supernova remnant has erupted in an enormous flare five times more powerful than any flare previously seen from the object. On April 12, NASA’s Fermi Gamma-ray Space Telescope first detected the outburst, which lasted six days.

The nebula is the wreckage of an exploded star that emitted light which reached Earth in the year 1054. It is located 6,500 light-years away in the constellation Taurus. At the heart of an expanding gas cloud lies what is left of the original star’s core, a superdense neutron star that spins 30 times a second. With each rotation, the star swings intense beams of radiation toward Earth, creating the pulsed emission characteristic of spinning neutron stars (also known as pulsars).

Apart from these pulses, astrophysicists believed the Crab Nebula was a virtually constant source of high-energy radiation. But in January, scientists associated with several orbiting observatories, including NASA’s Fermi, Swift and Rossi X-ray Timing Explorer, reported long-term brightness changes at X-ray energies.

“The Crab Nebula hosts high-energy variability that we’re only now fully appreciating,” said Rolf Buehler, a member of the Fermi Large Area Telescope (LAT) team at the Continue reading Flare States of the Crab Nebula

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What an Astronaut’s Camera Sees: International Space Station

An intimate tour of Earth’s most impressive landscapes… as captured by astronauts with their digital cameras. Dr. Justin Wilkinson from NASA’s astronaut team describes the special places that spacemen focus on whenever they get a moment.

We start with the coast of Namibia in southwestern Africa, the very dry desert coast of the Namib Desert. You can see a cloud band butting up against the shore and some straight sand dunes in the lower left of the picture. Yeah those are big red sand dunes that the astronauts say is one of the most beautiful sites that you can get when you’re flying.

Coming into the view on the left is an impact crater right in the middle of the picture, right about now and some wind streaks. We know where this area is because it’s a bit unique. We’ve got a major dune field coming into the picture on the left there: the Oriental Sand Sea, as it’s called in French, and on the top is the Isawan Sand Sea.

This is the island of Sicily with cloud over Mt. Etna, so you can’t quite tell there’s a big volcano in the middle of the picture right now. And there’s Continue reading What an Astronaut’s Camera Sees: International Space Station

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Space is exciting