INCREDIBLE 3-D FLY-THROUGH OF THE ORION NEBULA

The three stars of Orion's belt and the four tracing his sword are among the most recognizable signposts in the night sky. Astronomers have know for years that the middle "star" in Orion's sword--the Orion nebula--is actually an extremely dynamic system of young stars and the clouds and cocoons of gas and dust from which new stars are still being born.

The constellation Orion

clearly showing Orion's belt and sword

Credit: Mark Mathosian 

Astronomers and visualization specialists at NASA's Universe of Learning program have now gifted us with a remarkable 3-D fly-through of the Orion nebula based on visual images from the Hubble Space Telescope, infra-red images from the Spitzer Space Telescope and state-of-the-art 3-D modeling and image processing.

You can find four versions of the fly-through at this URL. They include one in visible light, one in infrared light, and shorter and longer versions combining the visible and infrared views.

 The Orion Nebula in visible and infrared light

Credit: StSci

Remember, this is not a Hollywood sci-fi mockup, but an accurate 3-D rendition using astronomy's best images of and data about the Orion Nebula. Given that the nebula is estimated to be 24 light-years across, these  video journeys are something no human could actually make; they provide a unique, almost god-like view. Sit back, turn on your speakers, and enjoy the trip.

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GALAXIES LIKE GRAINS OF SAND

The universe just got ten times more crowded.

Less than a century ago, astronomers believed that the Milky Way galaxy--our home galaxy--comprised the entire universe. In 1924, astronomer Edwin Hubble discovered galaxies, "island universes" far beyond the Milky Way. As telescopes got bigger and better, and eventually were sent into space, researchers estimated that the observable universe--the part of the universe from which light has had time to reach Earth--contained some 120 billion galaxies.

Hubble Ultra-deep field, 2014. Credit: NASA

Today, a team of researchers from NASA and ESA (the European Space Agency) released the results from a new and more accurate 3-D galactic census. The find that for every galaxy astronomers can see with today's telescopes, there are at least 10 that will be detected by the next generations of instruments.

"It boggles the mind that over 90% of the galaxies in the universe have yet to be studied," says the study's lead author, Christopher Conselice.

So it looks as though we live in a universe not with 120 billion other galaxies, but 1.2 trillion. With an average galaxy containing, say, 100 billion stars, that makes the star count around 10 to the 23rd power, or 10 with 23 zeroes after it.

It seems like pretty much every astronomical discovery, starting with Copernicus' shocking revelation in 1543 that Earth is not the center of the cosmos, has had the effect of pointing out that we're not quite as significant in the big scheme of things as we might like to think. 

The good news is that knowing that we're just the inhabitants of the third planet around one star out of a hundred billion in one galaxy out of a trillion does put our current worries--right down to the size of a particular presidential candidate's hands--into perspective.

(And hats off to British science fiction author, Brian Aldiss, for the evocative and prophetic title of his 1960 book, Galaxies Like Grains of Sand.)

Vast underground ice sheet found on Mars

NASA image shows water ice fading between October, 2008 and January, 2009

I've just finished listening to a NASA press conference announcing that nearly half of Mars has a layer of nearly pure ice just under its surface.

The NASA scientists estimate that this represents about one million cubic kilometers of ice, or about twice the amount of ice that covers Greenland here on Earth.

The Martian ice was exposed to view by meteorites that blasted out small craters--a few meters in diameter and from half a meter to two-and-a-half meters deep--and, much to the scientists' surprise, revealed a layer of 99 percent pure ice that they think ranges from 1 to 10 meters (33 feet) thick.

These underground ice sheets appear to extend from the Martian poles to about 45 degrees north and south--that is, halfway from each pole to the Martian equator.

Three different instruments in orbit around Mars on the Mars Reconnaissance Orbiter allowed the scientists to detect five newly formed craters, photograph bright, bluish-white material in or splashed out around them, material that quickly faded away during the Martian summer, and finally identify that material as nearly pure water ice by its spectrum.

"We found a beautiful water ice signature," said Selby Cull, from the Compact Reconnaisance Imaging Spectrometer for Mars team. "Crystal-clear-no-doubt-about-it water ice."

The ice is amazingly recent--around 10,000 years old--the scientists say. It dates from a period when Mars was wetter and had much more water vapor in its atmosphere than it does today.

According to the researchers, the discovery sheds light on the recent climate history of Mars, during which water vapor has shuttled out from and back to the polar regions as the Martian climate has warmed and cooled due to changes in the amount of sunlight the planet receives.

This plus earlier studies have led scientists to conclude that Mars had far more water in the distant past--several billion years ago--but has cooled and dried out over time. Some of the water is now locked up in minerals, some has been lost to space, and some remains in the form of ice.

In contrast, Earth has managed to keep most of its water.

Mars is now too cold, and its atmosphere is too thin, to allow liquid water to exist at the surface. However, these new findings suggest that water may still percolate underground, coalescing to form these newly discovered underground ice sheets.

Ironically, the Viking II spacecraft landed in the region where this ice was found in 1976, and scraped down into the soil, but not quite deep enough to find the ice.

"If Viking II had been able to dig down a few more inches, we could have made this discovery 30 years ago," said Shane Byrne, with the High Resolution Imaging Science Experiment.

The NASA scientists say they were not surprised to find ice under the surface of Mars, but were amazed to find that it was so pure. "We expected it to be a 50-50 mix of ice and dust," Byrne said. This has sent them back to their blackboards to try to explain what they found.

It may be decades or even centuries before humans set foot on Mars. The good news is that when we do get there, there will be plenty of water waiting for us just under Mars' cold and dusty surface.

Robert Adler
for the institute