For almost twenty years now, space cameras circling the planet Mars have sent back to Earth a remarkable treasure trove of revealing pictures of the Red Planet–our own tiny blue world’s near neighbor in space. These images of Mars unveil a surface etched with tiny valleys that have been sculpted into slopes, showing a similar shape to gullies that have been created by flowing water on earth. The presence of liquid water suggests the possibility–though by no means the promise–of the existence of life as we know it. Although the rust-red world with a butterscotch sky is one of the closest planets to our own in the Solar System, it has still managed to keep some very intriguing secrets to itself–waiting to be discovered by curious observers on earth, who are captivated by the sirens’ song that it is a possible abode for living v guard gas geyser creatures. In December 2016, a team of astronomers, using NASA’s Mars Reconnaissance Orbiter (MRO), reported that they had discovered the origin of mysterious–albeit non-living–Martian “spiders”. The team of planetary scientists propose that erosion-carved troughs that grow and branch out during the passage of many Martian years may be baby versions of the larger “spiders, ” which are radially patterned channels observed only in the south polar region of Mars.
The Martian polar caps are some of the most dynamic regions on Mars, growing substantially larger in winter, and retreating during the spring and summer. This is because a significant percentage of the atmosphere freezes out in the form of carbon dioxide ice (dry ice). Strange and alien dark spots, fans and splotches emerge as the south-polar carbon dioxide ice cap melts and retreats during the Martian spring and summer. Small radial channel networks are frequently associated with the location of dark spots.
Some of the most mysterious surface features on Mars are its so-called “spiders. ” Indeed, the Martian surface is crawling with “spiders”, and the strange “spiders” range in size from tens to hundreds of yards. Typically, many channels meet and then merge together at a central pit, forming surface features that look like the legs and body of a spider–a very big spider–with the channels resembling its legs, and the central pit its body. For about a decade, planetary scientists tried in vain to discover the origin of these very weird features. Finally, using MRO’s High resolution Imaging Science Experiment (HiRISE) camera, the team of planetary scientists succeeded in observing the year-to-year variations of these remarkable and intriguing features that crawl along the Martian surface.
We have seen for the first time these smaller features that survive and extend from year to year, and this is how the larger spiders get started. These are in sand-and-dune areas, so we don’t know whether they will keep getting bigger or will disappear under moving sand, ” explained Dr. Ganna Portyankina in a December 20, 2016 NASA Jet Propulsion Laboratory (JPL) Press release. Dr. Portyankina is of the University of Colorado, at Boulder. The JPL is in Pasadena, California.
The planet Mars dwells in the warm, well-lit regions of the inner Solar System, where our Star is bright enough to blaze in its butterscotch sky with its beautiful, blinding stellar glare. Mars is the fourth planet from our Sun, as well as the second-smallest planet in our Star’s family–after Sun-scorched Mercury, the innermost of our Solar System’s eight major planets.
Named after the Roman god of War, Mars is frequently called the Red Planet because of its rust-colored appearance, which is caused by iron oxide that is abundant on its surface. A terrestrial planet with a thin atmosphere, the surface features that Mars displays are hauntingly similar to the deserts, polar ice caps, and valleys of our Earth–as well as to the numerous impact craters that pock-mark our own planet’s large Moon.
The Martian rotational period, as well as its seasons, are also similar to those of Earth–as is its tilt that causes the seasonal variations. Mars also hosts Olympus Mons, which the largest volcano, as well as the second-highest known mountain in our Solar System. In addition, the Martian terrain displays one of the largest valleys in our Solar System–the Valles Marineris. The smooth Borealis basin that marks the Martian northern hemisphere covers an amazing 40% of the entire planet, and is thought to be a possible impact basin, left as a lingering scar from the primordial crashing together of two worlds.
Mars is circled by a duo of tiny moons, dubbed Phobos and Deimos, that are irregular in shape and resemble large potatoes. Some planetary scientists propose the two small Martian moons may have originally been born as asteroids inhabiting the main Asteroid Belt between Mars and Jupiter. However, the duo wandered away from their place of birth, only to be captured by the gravity of the planet that they now circle.
Mars is a fascinating world that has been made the target of a number of ongoing studies hunting for clues that ancient life may once have thrived there–as well as the possibility that Mars still hosts some small lingering tidbits of life. For this reason, astrobiology missions are being planned, including the Mars 2020 and ExoMars rovers.
The presence of liquid water is necessary for life as we know it to potentially evolve and flourish on distant worlds. Alas, liquid water cannot exist on the surface of Mars because of its low atmospheric pressure–with the exception of certain areas of lowest elevation, and here only for brief periods. The two polar ice caps of Mars appear to be composed primarily of water. The volume of water ice in the south polar Martian ice cap, if it were to melt, would be sufficient to cover the entire surface of the Red Planet to a depth of 36 feet. On November 22, 2016, NASA announced the discovery of a large quantity of underground ice in the Utopia Planitia region of Mars. Indeed, the amount of water that has been detected has been estimated to be approximately equal to the volume of water in Lake Superior.
At present, Mars is being visited by seven spacecraft. Five of these visiting spacecraft are in orbit: 2001 Mars Odyssey; Mars Express, MRO, MAVEN, and Mars Orbiter Mission. The two other spacecraft that are roaming around, exploring the surface of the planet itself, are the Mars Exploration Rover Opportunity and the Mars Science Laboratory.
The geysers that erupt on the Martian surface are areas where small amounts of gas and dust shoot out from surface cracks in the south polar region during the spring thaw. “Spiders” and dark dune spots–or araneiforms–are the two most easily observed types of features thought to result from these eruptions.
The Martian geysers are very alien structures, and they are different from any terrestrial geological phenomenon seen on our Earth. The reflectance (albedo), shapes, and mysterious “spidery” appearance of these surface features have been the source of numerous scientific hypothesis about how they formed and why. The theories proposed to explain these oddities range from variations in frosting reflectance, to explanations proposing certain biological processes. However, all of the current explanations that are being suggested, based on geophysical models, assume that there is some form of geyser-like activity on the Red Planet. The characteristics of these geysers, as well as the process that triggers their formation, are still a matter of considerable debate.
These bizarre features are apparently unique to the Martian south polar region, located in an area informally dubbed the “cryptic region”, at latitudes 60 to 80 degrees south and longitudes 150 degrees west to 310 degrees west. The approximately 1 meter deep carbon dioxide ice transition area–located between the scarps of the thick polar ice layer and the permafrost–is the region where there are clusters of geyser-like activity shooting out from the Martian surface.
The seasonal frosting and defrosting of the dry ice sheets create the dark dune spots with “spidery” channels, located beneath the ice, where “spidery” radial channels slice between the ground and the dry ice–giving it an appearance that hauntingly resembles spider webs. Ultimately, pressure accumulates in the interior, ejecting gas and dark basaltic sand or dust, which is ultimately deposited on the ice surface–creating the dark dune spots. This is a speedy process, that has been observed to occur in the time-span of only a few days, weeks, or months–a rapid growth rate that is unusual in geology, especially Martian geology. However, it has been proposed that the passage of many years would be necessary in order to carve the larger “spider”-like channels. Unfortunately, there is no direct data available to explain these strange and puzzling features, other than images obtained in the visible and infrared parts of the electromagnetic spectra.
The dark dune spots and “spiders” were discovered separately on images obtained from 1998 to 1999 by the Mars Orbiter Camera (MOC) aboard the Mars Global Surveyor (MGS). MOC was developed by Malin Space Systems, a private company that builds and operates space camera systems. Malin Space Systems is in San diego, California.
Planetary scientists originally thought that the dark dune spots and “spiders” were unrelated features because of their appearance. As a result, from 1998 through 2000 they were reported on separately by different research publications–with the first “jet” or “geyser” models developed and refined from 2000 onwards.
Malin Space Systems personnel were the first to name these very odd Martian surface features “spiders”. One of the most interesting “spider” images–as well as one of the first–was discovered by Mars researcher Greg Orme in October 2000. Mr. Orme, of Brisbane, Australia, is the owner of Computers Fast. The weird shape and rather complex appearance of these “spider webs”, and their accompanying spots, created a considerable amount of speculation about how they had formed. The first observations revealed that during the following Martian years, about 70% of the spots appear at precisely the same place. Furthermore, preliminary statistical studies obtained between September 1999 and March 2005 suggested that the dark dune spots and “spiders” are related features that result from the cycle of carbon dioxide ice condensation and sublimation. It was also originally proposed that the dark spots were merely warm patches of bare ground, but thermal imaging during 2006 showed that the temperature of these structures is just as frigid as the ice that coats the region. This suggested that the spots were really a slender layer of dark material lying on top of the carbon dioxide ice–and were being kept well-chilled by it. However, shortly after their first detection, they were discovered to be negative topographical features–that is, they were seen to be radial troughs or channels of what is currently thought to be geyser-like vent systems.
The geysers’ two most notable features (“spider” channels and dark dune spots) show up at the start of the Martian spring on dune fields that are covered with carbon dioxide ice–mainly in ridges and slopes of the dunes. However, at the beginning of the Martian winter, they vanish. The shape of the dark spots is generally round, but on the slopes it is usually elongated, sometimes with streams–possibly composed of water that accumulates in pools.
According to the recent MRO study, Martian dunes are apparently a factor causing the baby “spiders” to form. However, the dunes may also help many of the little spiders survive through the centuries, thus providing them with sufficient time to grow and become large “spiders”. The amount of erosion necessary to sculpt a typical Martian “spider”, at the rate calculated from observing active growth of these smaller troughs, would need the passage of a thousand Martian years, according to an estimate made by Dr. Portyankina and co-authors in a paper published in the planetary science journal Icarus. One Martian year is the equivalent of about 1. 9 Earth-years.
“Much of Mars looks like Utah if you stripped away all vegetation, but ‘spiders’ are uniquely Martian landform, ” commented Dr. Candice Hansen in the December 20, 2016 JPL Press release. Dr. Hansen is of the Planetary Science Institute in Tucson, Arizona, and a co-author of the Icarus report.
Dry ice does not form naturally on earth. However, Mars is an entirely different world. On Mars, sheets of dry ice naturally coat its surface during the winter in regions that are close to both poles–including the south-polar areas that are covered with “spidery” terrain. During every Martian spring, strange dark fans form in these very regions. These dark alluvial fans are gently sloping wedges composed of sediment deposited by flowing water.
Dr. Hugh Kieffer of the Space Science Institute in Boulder, Colorado, proposed that the process linking the dark fans and “spidery” terrain begins when spring sunshine cuts through the ice and warms up the ground underneath. This results in some of the carbon dioxide on the bottom of the sheet of dry ice to melt and turn into a gas. The imprisoned gas finally creates a powerful pressure that ultimately forms a crack in the sheet of dry ice. At this point, gas erupts out, and gas trapped beneath the ice rushes screaming to the vent, accumulating particles of dust and sand as it flees to the crack where it can escape. This process erodes the ground. It also bestows the geyser with particles that tumble back to the planet’s surface, downwind–and thus produce the dark fans of the Martian spring.