Monthly Archives: September 2011

Pay a Visit to Vesta

Can’t see the video below? Click here.

Here’s a great video released by JPL taking us on a virtual tour of the asteroid Vesta, from the point of view of NASA’s Dawn spacecraft. It’s a shape model of Vesta, mapped with actual images acquired by Dawn during its approach and orbit of the 550-km (340-mile) -wide protoplanet.

Once little more than a fuzzy point of light to astronomers, Dawn has revealed Vesta to be quite a fascinating little world, with many unique and unexpected landforms like mountains, steep scarps, long grooves, scattered light and dark splotches and curious clusters of “wormlike” scratches. And all this in just three months of orbit… not too shabby!

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Mercury’s Curious Hollows

Hollows in Sander Crater.

As part of a wealth of new information presented today by the MESSENGER science team, this image shows the interior of Sander Crater, located within Mercury’s vast Caloris Basin. Areas seen as bright spots in previous lower-resolution images have been revisited by MESSENGER once it entered orbit and began its science mission. The bright areas turned out to be unexpected landforms named “hollows”, clustered irregularly-shaped depressions with bright interiors and halos. Hollows have since been found in many areas across Mercury, although the exact process that creates them is not exactly known. They may be the result of the erosion of volatile material by solar wind.

More hollows in Raditladi Basin

The lack of craters within the hollow clusters seems to indicate that they are relatively young features.

“Analysis of the images and estimates of the rate at which the hollows may be growing led to the conclusion that they could be actively forming today,” says David Blewett, a staff scientist at the Johns Hopkins University Applied Physics Laboratory (APL). “The old conventional wisdom was that ‘Mercury is just like the Moon.’ But from its vantage point in orbit, MESSENGER is showing us that Mercury is radically different from the Moon in just about every way we can measure.”

Seems that MESSENGER’s first six months around Mercury have been very productive ones! It will be interesting to see what else it will discover as the only spacecraft ever to orbit the first rock from the sun.

Read more about this and other recently-announced findings from MESSENGER here.

Image: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Did Earth Once Have Two Moons?

Our Moon. It lights up our nights, governs our tides and has inspired millions — perhaps billions -– of people throughout history to contemplate its nature, its influence on our lives (if any) and, of course, where it may have come from.

The currently accepted theory is that over four and a half billion years ago our newly-formed planet was impacted by a Mars-sized body, a catastrophic collision that flung molten bits of Earth’s mantle into space and created a ring of debris. This gradually gathered together to create our Moon… but, according to some new models created by researchers at UC Santa Cruz, it may have actually created two moons. But if this is indeed the case, what happened to the other one?

Read more on my article at Discovery News.

Ripples in the Sky

Here’s something interesting…

This Saturday I was looking at some timelapse video from the Canada-France-Hawaii Telescope’s Cloudcam… those are beautiful in their own right, but really I was interested in seeing if there was any visual of the reentering UARS. After doing some time-zone math, I realized that the satellite would be reentering before it was really dark over Hawaii, but I did see something unusual in this sequence from the 23rd-24th:

If you notice, around 21:33 HST (about 30 seconds in) in the video, there are some “ripples” high in the atmosphere visible in the upper left of the frame. These extend for some time before dissipating completely. Could that be a “shockwave” from the reentering UARS, further north and east on the globe? Based on this trajectory map, UARS could have reentered the atmosphere not too far from that site.

NASA scientists still aren’t exactly sure where and when UARS came down, but it’s suspected all remains went into the Pacific Ocean west of Canada.

I’m looking into this with those much more specialized in such things than I am. Stay tuned…

Video credit: Canada-France-Hawaii Telescope (Check out the original HD version on the site here.)

UPDATE: I am being told by a couple of experts that this may be “just” a case of high-level cirrus clouds, or else something created by the video compression. Not sure, I think I am going to look into it a bit further.

UPDATE 2: It’s 99% surely cirrus clouds. After hearing back from several reputable expert sources, and seeing where the UARS eventually did enter the atmosphere (off the eastern coast of Africa) it’s definitely not shock waves. Oh well. But that’s how you find things out… asking the right people their thoughts! 

 

On Top of the World

ISS astronaut Ron Garan peers out if the Station's cupola at the Earth below.

In what may be the best single representation of the visual feast of images we have enjoyed from Expedition 28 flight engineer Ron Garan during his 5 1/2 month stay aboard the ISS, this amazing image shows him inside the Station’s cupola as he took his last images of Earth before departing.

I must say, if anything embodies the blurring line between science fiction and science reality that’s become a daily part of our lives… this is it.

Thanks to Ron for sharing this on his Twitter feed! Follow him on Twitter @Astro_Ron, and be sure to check out his website FragileOasis.org and become a member there.

Image has been rotated 90º from the original: twitpic.com/6qnsgy

Credit: NASA

UPDATE 4/16/12: Ron shared this post on his Google+ page… he says “I call it ‘Downside Up Downunder’.” Thanks again Ron!

Rolling Stones in the Lake of Death

Boulders rest in a crater valley on the Moon

No, it’s not the title of a B-movie starring Keith Richards, it’s an image of lunar boulders resting in a line within a valley on the Moon. This valley, located in the central peak of Bürg crater, is filled with boulders ranging up to 70 feet across that have rolled downhill from either side. The boulders’ paths are evident from the trails they left behind in the lunar soil (regolith).

Some boulders took a quicker, more linear route downhill while others made more leisurely and meandering paths.

The crater is located within a lunar region called Lacus Mortis, or “Lake of Death”.

This image is a section from a Lunar Reconnaissance Orbiter image; see the full scan here.

Credit: NASA / GSFC / Arizona State University.

As The World Turns

Today is the autumnal equinox, when the Earth receives sunlight at its most direct angle relative to its equator and poles. As Earth orbits around the Sun over the course of a year, its axial tilt causes the angle of solar illumination to change – a predictable and regular change, but a change nonetheless. This is what gives us our seasons and affects our climate zones and weather and basically how life on our planet has evolved to be what it is, where it is! Fascinating stuff, although admittedly a little hard to envision.

This helps:

The video was taken with the European METEOSAT-9 Earth-observing satellite – or rather, an animation made up of images of our planet taken over a single year. You don’t see the Earth itself move, but the terminator line – the edge of the shadow between the day side and the night side – clearly changes angle through the animation.

Since the angle of the sunlight isn’t changing, the realization is that the Earth itself is what’s moving! Very cool.

Originally posted by Phil Plait at the BadAstronomy blog… read more on Universe Today here.

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