New Images Suggest More Recent Lakes on Mars

Image of a channel between putative lakes from the Context Camera (CTX) onboard NASA’s Mars Reconnaissance Orbiter (MRO).

Modern Mars is frigid and dry, but new evidence suggests that in some locations on the equator there may have been lakes as recently as 3 billion years ago.

Researchers from Imperial College London and University College London studied images from the context camera (CTX) on NASA’s Mars Reconnaissance Orbiter (MRO) of several flat-floored depressions in Ares Vallis, near the martian equator.

Previously these depressions were thought to be due to the collapse of the surface as ground ice sublimated directly to gas, but CTX images reveal small channels connecting the depressions, suggesting that water flowed between them. Similar features can be found in “thermokarst” landscapes in Alaska and elsewhere, where permafrost is melting to create lakes and streams.

To determine the age of the features, the scientists counted more than 35,000 craters in the area. Assuming that the current surface was continuously exposed to impacts from space since it was emplaced, the density of craters points to an age of roughly three billion years.

Previously, it was thought that Mars dried up between 4 and 3.8 billion years ago, but if the cratering age from this study is correct, these new results suggest at least brief periods later in martian history when lakes could exist.

The lead author, Dr Nicholas Warner, from the Department of Earth Science and Engineering at Imperial College London, said: “Most of the research on Mars has focused on its early history and the recent past. Scientists had largely overlooked the Hesperian Epoch as it was thought that Mars was then a frozen wasteland. Excitingly, our study now shows that this middle period in Mars’ history was much more dynamic than we previously thought.”

It is not clear how long-lived the lakes were, but Warner and colleagues suggest that they may have served as oases for life in an otherwise inhospitable world. They also suggest that these lakes would be an interesting landing site for future robotic missions.

What’s the next step? The researchers plan to study other equatorial areas, including the mouth of Ares Vallis and Chryse Planitia to see how widespread the putative lakes were.

Kaguya Discovers a Lava Tube on the Moon

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Future lunar astronauts may want to brush up on their spelunking skills: the first lava tube has been discovered on the moon.

In a recent paper published in Geophysical Research Letters, Junichi Haruyama and colleagues report that they have discovered a mysterious hole in the lunar surface in high resolution images from the Kaguya spacecraft. The hole is 65 meters in diameter and is located in the volcanic Marius Hills region on the near side of the moon, right in the middle of a long sinuous rille. Sinuous rilles are thought to be formed by flowing lava, either on the surface or in enclosed lava tubes.

Of course, there are a lot of ways to form a hole in the surface of the moon. The most obvious is with an impact: the moon has literally been battered to pieces over the years by rocks from space. Couldn’t this hole be a fresh impact crater? Nope. Haruyama’s team observed the hole nine separate times, at various illumination angles, and even when the sun was almost directly overhead it looked mostly black, suggesting that it is very deep. They calculate a depth of around 88 meters, so the hole is deeper than it is wide. No impact crater is like that.

Four different views of the lava tube skylight at varying sun angles. Arrows indicate the direction of incident sunlight (I) and the viewing direction (V). Image credit: JAXA/SELENE
Four different views of the lava tube skylight at varying sun angles. Arrows indicate the direction of incident sunlight (I) and the viewing direction (V). Image credit: JAXA/SELENE

Another possibility is that the hole is due to some sort of volcanic eruption, but there is no sign of volcanic deposits like lava flows or ash emanating from the hole. The hole is isolated, so it isn’t likely to be due to a fracture in the lunar crust either – you would expect such a fracture to form a chain of holes.

Haruyama’s team concluded that the most likely explanation is that the hole that they discovered is a “skylight” – a location where the roof of a lava tube collapsed, either when the lava filling the tube flowed away, or later in the moon’s history due to an impact, moonquake, or tidal forces from the Earth. If it is a lava tube, their calculations based on the multiple images of the hole show that the tube could be 370 meters across.

Lava tubes are important in understanding how lava was transported on the early moon, but they are not just a scientific curiosity: they may also provide valuable refuges for future human explorers. The surface of the moon is not protected from the harsh radiation of space by a magnetic field or a thick atmosphere, so a long term human presence would be most feasible if astronauts could spend most of their time shielded underground. Digging a hole large enough to fit an entire moon colony in it would be a huge engineering challenge, but lava tubes could provide ready-made locations for a well-shielded base, making future astronauts the most technologically advanced cave-dwellers in history.

Black Hole Drive Could Power Future Starships

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What would happen if humans could deliberately create a blackhole? Well, for starters we might just unlock the ultimate energy source to create the ultimate spacecraft engine — a potential  “black hole-drive” —  to propel ships to the stars.

It turns out black holes are not black at all; they give off “Hawking radiation” that causes them to lose energy (and therefore mass) over time. For large black holes, the amount of radiation produced is miniscule, but very small black holes rapidly turn their mass into a huge amount of energy.

This fact prompted Lois Crane and Shawn Westmoreland of Kansas State University to calculate what it would take to create a small black hole and harness the energy to propel a starship. They found that there is a “sweet spot” for black holes that are small enough to be artificially created and to produce enormous amounts of energy, but are large enough that they don’t immediately evaporate in a burst of particles. Their ideal black hole would have a mass of about a million metric tons and would be about one one-thousandth the size of a proton.

To create such a black hole, Crane and Westmoreland envision a massive spherical gamma-ray laser in space, powered by thousands of square kilometers of solar panels. After charging for a few years, this laser would release the pent-up energy equivalent to a million metric tons of mass in a converging spherical shell of photons. As the shell collapses in on itself, the energy becomes so dense that its own gravity focuses it down to a single point and a black hole is born.

The black hole would immediately begin to disgorge all the energy that was compressed to form it. To harness that energy and propel a starship, the black hole would be placed at the center of a parabolic electron-gas mirror that would reflect all the energy radiated from the black hole out the back of the ship, propelling the ship forward. Particle beams attached to the ship behind the black hole would be used to simultaneously feed the black hole and propel it along with the ship.

Such a black hole drive could easily accelerate to near the speed of light, opening up the cosmos to human travelers, but that’s just the beginning. The micro-black hole could also be used as a power generator capable of transforming any matter directly into energy. This energy could be used to create new black holes and new power generators. Obviously, creating and harnessing black holes is not an easy undertaking, but Crane and Westmoreland point out that the black hole drive has a significant advantage over more speculative technologies like warp drives and wormholes: it is physically possible. And, they believe, worth pursuing “because it allows a completely different and vastly wider destiny for the human race. We should not underestimate the ingenuity of the engineers of the future.”

Article available on ArXiv.
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