October 23, 2017

25.06.10- MRO and the Case of the Martian Spirals.

 

The NPC of Mars. (Credit: NASA/Caltech/JPL/E. DeJong/M. Stetson).

The NPC of Mars. (Credit: NASA/Caltech/JPL/E. DeJong/M. Stetson).

 

   Scientists may have solved the formation of one of the more curious features on Mars; the formation of its polar ice spirals. First spotted by NASA’s Mariner 9 spacecraft in 1972, these strange swirling patterns etched in the polar ice caps have remained a mystery. For example, the ice formation actually tends to form against and creep into the prevailing winds. Now Jack Holt and Isaac Smith at the University of Texas have used the Mars Reconnaissance Orbiters (MRO) Shallow Subsurface Radar to shed new light on the mystery. MRO’s radar can penetrate layers of ice that have accumulated over the millennia. During the Viking missions, researcher Alan Howard of the University of Virginia first proposed a mechanism for how these spirals could form via wind sweeping downslope and picking up water vapor and ice crystals and subsequently depositing them on the leeward or sun shadowed side on the opposite side of a trough. This process would be self replenishing as the spiral crept forward, much like glacial movement on Earth. This Sun-wind mechanism never gained wide spread acceptance, however, until close scrutiny by the MRO. The Coriolis force generated by the rotation of Mars adds the final touch, creating the final spiral structure. So why don’t we see similar structures in the polar regions of Earth? In the Arctic and Antarctic, more complex forces come into play; here, local topography overpowers the Coriolis force (remember, Mars, while having a day similar in length to the Earth, is much tinier) and shapes the force of the wind. The findings may also explain a prominent feature in the Martian northern polar cap; the Chasma Boreale, a long gash burrowed deep into the ice. It appears as if this canyon is related to a single ice melt event from 5 to 10 million years ago, and prevailing winds have not allowed for deposition of ice ever since. MRO has even discovered a second unknown chasm as well. The history of the formation of the polar caps all tie in to the Martian climate puzzle; a picture of the tiny world’s climate history is rapidly evolving into a unique story, one that parallels our own but diverges from it as well. What new mysteries does the Martian landscape hold?

04.03.10: A Close Flyby of Phobos.

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Phobos on a pass of Mars Express last July. (Credit: ESA/DLR/FU Berlin/G. Neukum).

  

 The European Space Agencies’ (ESA) Mars Express orbiter completed the closest ever flyby of the misshapen Martian moon, Phobos, but don’t expect to see any mind blowing pictures…yet. Part of a series of 12 flybys, last nights’ pass skimmed to worldlet by 67 km, allowing its feeble gravity to deflect the space probe by a tiny but perceptible amount. This will allow engineers on the ground to get an idea of the internal density and composition of Phobos. But to do so, all instruments must be silent, so scientists can isolate minute oscillations on the probes carrier signal via the Doppler Effect. But take heart; Mars Express will further probe the moon on future passes via its MARIS radar, and will have its cameras switched on during next weeks’ March 7th pass…expect more cool pics soon!

14.10.09: The Earth-Moon System as viewed by HiRISE.

The image above floated through our tweet-o-sphere yesterday, thus prompting today’s news post. HiRISE, NASA’s High Resolution Imaging Science Experiment aboard the Mars Reconnaissance Orbiter(MRO) is the spacecraft that you’re probably not following, but should be. In orbit about the Red Planet since early 2006, its been transmitting some pretty mind blowing images, all definitely worth a daily peek! Housing a 0.5 meter reflecting telescope which would be the envy of any backyard astronomer, its the first true “spy satellite” quality orbiter that we’ve fielded about Mars. Able to resolve targets about 0.3 meters across, some of the highlights have included stunning views of the polar caps and dunes, snapshots of the Opportunity and Spirit landing sites, and even catching the Phoenix Lander in descent! In fact, eagle-eyed desktop amateurs may even prove successful it divining the fate of the many (more than half!) errant Mars-bound landers over the years. But as is often the case with space exploration, we travel millions of miles to find…ourselves. Some of the most memorable images are actually those of the Earth, whether its “Earth-rise” aboard Apollo 8 or the “Pale Blue Dot” as viewed from Voyager 1, images such as these and the HiRISE pic above of our tiny home remind us how special our place is. Snapped back in 2007, it shows us that the Earth is not only a pretty, but dynamic place were things are happening. Mars is tiny and cratered, and through a backyard telescope, generally yields little detail. Venus, although dazzling, is perpetually shrouded in sulfurous cloud. Not so with the Earth. Cloud cover changes, the surface shows a variation in sea, land, and seasonal growth, and at night, an experienced telescopic eye might just pick out the lights of cities, evidence of human activity. Views like this always remind me of Arthur C. Clarke’s little known but classic short story Report on Planet Three, where Martian scientists argue that life couldn’t exist on Earth! Clarke wryly points out that life elsewhere may not be remotely Earth-like. I personally can’t wait to spread my telescope tripod legs out under a night under Martian skies; and without a doubt, the slender crescent Earth-Moon duo will be my first astronomical target!