Robots To Go Spelunking In Martian Caves?

Robots that rappel, hop or lower themselves by tether into Martian skylights could reshape the hunt for life beyond Earth.

(A skylight opens into an underground cavern on the slopes of Mars’ Pavonis Mons volcano, as observed by NASA’s Mars Reconnaissance Orbiter. Credit: NASA/JPL-Caltech/Univ. of Ariz.)

“Scientists are beginning to sketch out plans for NASA’s new Mars rover Curiosity to climb Mount Sharp, but future robots may have a more direct way to access the planet’s history books.  Recent discoveries of ‘skylights’ (pictured here) and lava tubes on the surface of Mars, as well as the moon, are sparking the development of robotic probes that can descend into caves and explore tunnels.”

“Curiosity’s landing site inside an ancient impact basin was selected because of the three-mile high mound of layered rock, known as Mount Sharp, rising from the crater’s floor… An even richer treasure trove may be hidden underground, where potential habitats would be more shielded from the radiation that constantly blasts the planet’s surface.”

There’s every reason to think caves exist on Mars, and the “skylight” phenomenon seen from orbit provides ample evidence.  What are they?  That we see them mostly on the slopes of Mars’ giant shield volcanoes likely tells us that they’re probably like “skylights” seen on the slopes of terrestrial volcanoes.  Here’s a photo of one at Kilauea in Hawai’i, with some humans for scale:

(Credit: Martin Ruzek; USGS Hawaiian Volcano Observatory)

Skylights are windows into lava tubes, structures in which molten rock flows in defined channels below ground.  Occasionally the thin, rocky “ceiling” above the tube collapses, allowing a view of the inside.  If we could somehow carefully lower a probe through a skylight into a lava tube on Mars, we could potentially follow its course for miles, and get an up-close look at past volcanic processes on Mars.

But what about more familiar caves?  Think of the grand underground chambers and delicate formations of cave systems like Carlsbad, Mammoth, or Wind.  What do all these caves have in common?  Water.  And lots of it.  That’s something Mars doesn’t currently have much of, at least not in a liquid state.  But there’s ample evidence that Mars once had lots of water.  On Earth, caves take millions of years to form; there may have been sufficient time early in Mars’ history to make them, before it lost its water to space or climate change locked it away as ice in its interior.  If they exist, these caves would be harder to find, because their natural entrances may well not be visible to orbiting spacecraft.

Why should we look for water-formed Martian caverns?  They may preserve evidence of past life.  If connected to geothermal hot springs, underground caves may have provided both shelter from harsh ultraviolet light exposure as well as a liquid environment after outside water froze.  Even if life were once relatively abundant in Mars’ ancient oceans, it may well have gone extinct as those oceans disappeared, and caves offer a safe harbor where it could “hide out” for some unknown length of time — at least until the caves dried up.  So while no Mars missions have found indisputable proof of current (or past) life on Mars at the surface, we may one day find it in the deep, dark recesses of a Martian cave. -JCB

Caveat Spectator: Why Science Can Benefit From Image Fakery

A couple of Mars-related photos have been making the rounds in recent days, both on Tumblr and in the media more generally.  Here’s one that seems to purport to being a Martian sunset and compares it to a scene from Star Wars Episode IV:

It’s a fake.

Here’s another, showing the claimed view of in the Martian sky from an unnamed NASA rover, complete with Earth, Venus, and Jupiter as a chain of bright “stars” in its dusky sky:

It, too, is fake. (The inestimable Phil Plait has written a nice blog post about its impossibility, and another about the double-sunset.)

It’s at once difficult and easy to understand why images like these periodically make the rounds.  They’re not immediate impossibilities or intended as humor, unlike recent depictions of the first images radioed back from the Curiosity lander.  Most people, after all, can tell that Marvin the Martian popping up in a Curiosity frame is funny (especially when he’s complaining about being usurped by Mohawk Guy).  But they know it’s not real. 

Sometimes the real deal is presented as real, but the context gets confused.  The topmost image in this post is cropped from the one below, which is in fact real:

Taken by the NASA Spirit rover in 2005, it popped up again in the hours after Curiosity’s thrilling descent to the Martian surface last week, held up as the “first image” Curiosity returned to Earth.  It was believed by many to be the real deal; Gawker even posted an article titled: “No, This Isn’t The First Picture From The Mars Curiosity Rover”.  

Why do fake (or out-of-context) images have legs sufficient to allow them to run circles around the media — and now, around the world in seconds, thanks to the miracle that is the Internet?  Two ideas:

1. Sensational images play to our sense of imagination.  ”What if” is something that’s essential to the human experience, fueling both the artistry of fiction and eminent solutions to very real, complex problems.  The “double sun” depicted on the fictional Tatooine is not all that crazy; in fact, most stars in the universe are probably part of multiple star systems.  Who hasn’t wondered what Earth’s skies would look like in such circumstances?   A little fantasy sparks the same curiosity that compels us to explore this world — and others.

2. Realistic (but fake) images play to our sense of experience.  The real Martian sunset above is amazingly “real”; it could have easily been taken from some high desert on Earth on a particularly dusty day.  It’s readily comparable to sunset scenes in our own lives.  Suddenly, Mars isn’t a foreign, far-off world at all: it is a place with an imminence about it that challenges us to compare the scene to our own home in the Universe.  Of course, the hope is that people recognize that our solar system has only one star, not two, and therefore recognize that the “Star Wars” image can’t possibly be real.

What can this teach us about the interplay between science and our society? 

Some science writers breathe deep sighs at the prospect of having to explain away yet more digital fakery.  But I argue that we actually need these images in our society. They offer teachable moments in which we can grab hold of the viewer’s sense of both imagination and experience, step in with the correct information, and lead the way to the science.  Then discovery can take over, lighting the fire of further curiosity and evaluation — and more discovery.  

Public understanding of astronomy, and of science in general, can benefit by using faked images as a way to calibrate people’s “hoax detectors”.  Skepticism can exist comfortably alongside fantasy; our job as science enthusiasts is to reinforce the distinction between the two, as well as to promote the idea that the truths of science are often even stranger (and more exciting) than the best fiction.

Pluto Now Has Five (Yes, Five) Moons Observations made with the Hubble Space Telescope in just the past two weeks have revealed yet another moon in the Pluto system: S/2012 P 1, aka “P5” (circled, above).  This wayward chunk of ice and rock may be no more than about 15 miles in diameter, the size of a small city, and irregularly shaped.  Why should anyone care how many moons this “former” planet has?  Because a spacecraft from Earth is on its way to give us our first close-up view of this distant moon — the New Horizons mission, arriving in 2015.  We’ll be in largely uncharted waters, and the discovery of more Plutonian moons means that even smaller ones may exist that we can’t see from Earth.  That makes for a potentially dangerous flyby, although we will be as prepared as we can to visit this totally unfamiliar place.  There are new discoveries to be made right here, in our own Solar System, still.  -JCB
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Pluto Now Has Five (Yes, Five) Moons

Observations made with the Hubble Space Telescope in just the past two weeks have revealed yet another moon in the Pluto system: S/2012 P 1, aka “P5” (circled, above).  This wayward chunk of ice and rock may be no more than about 15 miles in diameter, the size of a small city, and irregularly shaped.  Why should anyone care how many moons this “former” planet has?  Because a spacecraft from Earth is on its way to give us our first close-up view of this distant moon — the New Horizons mission, arriving in 2015.  We’ll be in largely uncharted waters, and the discovery of more Plutonian moons means that even smaller ones may exist that we can’t see from Earth.  That makes for a potentially dangerous flyby, although we will be as prepared as we can to visit this totally unfamiliar place.  There are new discoveries to be made right here, in our own Solar System, still.  -JCB

(via discoverynews)

Venus 12 Days After Transit ImageSouce CCD and 16 inch Ritchey–Chrétien telescope. 3 min video processed with Registax software. (Credit & Copyright: Dean Salman / National Optical Astronomy Observatoroes (NOAO) / Association of Universities for Research in Astronomy, Inc.)
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Venus 12 Days After Transit

ImageSouce CCD and 16 inch Ritchey–Chrétien telescope. 3 min video processed with Registax software.

(Credit & Copyright: Dean Salman / National Optical Astronomy Observatoroes (NOAO) / Association of Universities for Research in Astronomy, Inc.)

Giant celestial disk hard to explain

About 80 light-years away, an enormous, dusty ring swirls around a sunlike star, with a defined inner edge that is probably sculpted by a planet orbiting at 140 times Earth’s distance from the sun.  A planet located so far from a sunlike star presents an astronomical conundrum.

(Hubble Space Telescope images of the star HD 202862 at two roll angles of the telescope.  The top panels show the original images; the bottom panels show the same view after software subtraction of the star’s light itself, revealing the faint, newly-discovered debris disk.  Credit: J. Krist et al./Astronomical Journal)

“‘How do you get a planet out that far? We don’t know how to form something out there,’ astronomer Karl Stapelfeldt of NASA’s Goddard Space Flight Center in Greenbelt, Md., said on June 14 at the 220th Meeting of the American Astronomical Society.  Stapelfeldt and a team led by John Krist of the Jet Propulsion Laboratory in Pasadena, Calif., used the Hubble Space Telescope to study 10 stars suspected of hosting large debris disks. Hubble saw a ring around only one, HD 202862, which resides near the southern constellations Grus and Microscopium.”

“Everything about the dusty circle — the biggest ever observed around a solar cousin — is huge. In places, the ring itself is 70 times wider than the Earth-sun distance, called an astronomical unit. From end to end, the debris disk is roughly 400 astronomical units long — larger than the well-known ring surrounding the star Fomalhaut. Like that ring, the newly observed one is also groomed by a celestial gardener — the planet lives about 140 astronomical units from HD 202862.”

“Such distantly orbiting planets challenge theories describing planet formation, especially around sunlike stars. Debris disks around these stars don’t contain enough material to grow a planet so far away. ‘The formation of wide-orbit planets is particularly not well-understood,’ says astrophysicist Aaron Boley of the University of Florida, who studies the Fomalhaut system and its far-flung ringscaping planets.  ’To build a complete understanding of planet formation, we must understand the architecture of planetary systems, which includes planets that are at very large stellar separations.’”

“Both Boley and Krist’s team suggest that the planet living around HD 202682 may have formed closer to the star, then migrated outward. But, Stapelfeldt says, that process would have had to be unusually gentle. ‘If you did something violent and you threw the planet out there, its gravity would tear up the ring,’ he said. ‘You wouldn’t expect to have something like this left over.’”

(The scientific paper reporting this result, recently posted to astro-ph, can be found here. -JCB)

Venus Transit in hydrogen alpha light, 5 June 2012 (Credit & copyright: Gilbert A. Esquerdo)
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Venus Transit in hydrogen alpha light, 5 June 2012

(Credit & copyright: Gilbert A. Esquerdo)

Transit Of Venus 5 June 2012 Seen in projection at the UW Space Place, Madison, WI
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Transit Of Venus 5 June 2012

Seen in projection at the UW Space Place, Madison, WI

View Today’s Venus Transit Online

So you say it’s cloudy where you live today, or you don’t have the proper eye protection required to see the event, but you still want to see the historic Venus Transit? 

The Interwebz are here to save you.  

A number of online resources are available, including telescopes broadcasting live feeds of the event:

Also, during the transit, check out what space-based observatories are seeing:
Enjoy!

(with thanks to Professor Astronomy and Sky & Telescope for the links)

Venus approaching the Sun, 29 hours before the transit. Refraction of sunlight through its atmosphere produces the near-complete ring of light. (Credit: Daniele Gasparri, Bologna University, Italy)
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Venus approaching the Sun, 29 hours before the transit. Refraction of sunlight through its atmosphere produces the near-complete ring of light.

(Credit: Daniele Gasparri, Bologna University, Italy)

The Disappearing Black Drop

Observers of historical transits of Venus have observed the black drop effect — but will you?

(This series of images shot from Singapore shows the possibility of a black-drop effect.  Credit: Joseph Tey)

“After the 2004 transit of Venus, observers were puzzled by the appearance (or lack thereof) of the black-drop effect, the dark patch that appears to connect Venus with the dark sky past the edge of the Sun, sometimes giving Venus a teardrop shape. The black drop was widely observed and commented on in the 18th and 19th centuries. So why, in 2004, did some people not see it at all?”

“‘Some of it may be a matter of degree,’ says Jay Pasachoff (Williams College). He says his study with Glenn Schneider (University of Arizona) of space-based images of the 1999 and 2003 Mercury transits shows that the telescope’s optics and resolving power are a factor in the black-drop effect. But they discovered that the Sun’s limb darkening— the fact that the Sun’s edge is darker than its center — is another important contributor. ‘So it’s not a surprise that big telescopes that have a better point-spread function don’t show a black drop effect.’”

(The ‘black drop effect’ — an unexpected “neck” of darkness that seems to connect the black sky to the disc of either Venus or Mercury during solar transits — was at times attributed to everything from refraction of light in the atmospheres of those planets to the imagination of observers’ minds.  Now we know that at least the effect is real, but it is the result of several factors conspiring together, including imperfections in the way telescopes image light.  What will telescopic observers see on Tuesday? -JCB)

(Australian watchmaker F. Allerding recorded the “black-drop” effect as the silhouette of Venus prepared to exit the Sun’s disk on December 9, 1874. He observed through a 3½-inch refractor.  CredIt: Institute for Astronomy, Univ. of Vienna.)