In the brightly lit, golden inner region of our Solar System, where our Sun’s streaming stellar fire can reach with its tender warmth and lovely light, the Red Planet Mars circles our Star. Perhaps no other planet has captured the human imagination more than Mars, the fourth major planet from our Sun, because we have long recognized it as a world capable of hosting life as we know it. However, despite being Earth’s near-neighbor in our Solar System, Mars has nevertheless managed to keep some very intriguing, ancient secrets well-hidden from the prying eyes of curious observers. In March 2016, a team of planetary scientists released their research findings suggesting that the surface of Mars tilted by 20 to 25 degrees 3 to 3.5 billion years ago. This catastrophe was caused by a tremendous volcanic structure, the Tharsis volcanic dome, which is the largest of its seething, eruptive kind in our Solar System. Because of the extraordinary mass of this volcanic structure, it caused the outer layers of Mars-its crust and mantle-to rotate around its core!
According to the new study, massive volcanic eruptions from this region on Mars produced so much lava that it pushed the entire surface of the Red Planet to such an extent that its north and south poles were shifted to different positions. Tharsis hosts the largest volcanoes in our Solar System: Arsia Mons, Pavonis Mons, and Ascraeus Mons–which are collectively termed the Tharsis Montes. All three enormous volcanos are shield volcanoes. A shield volcano is usually constructed almost entirely of fiery, liquid magma flows. These volcanoes are named for their immense size and low profile, that resembles an ancient warrior’s shield lying on the ground. These truly awe-inspiring volcanic structures are caused by the enormous amount of lava they erupt. Indeed, the study suggests that the eruptions on Tharsis caused such dramatic geological changes on the Martian surface, that it completely altered its geological history. The research further indicates that eruptions at Tharsis, that began 3.7 billion years ago, lasted for about two million years.
The discovery of this extraordinary shift alters the scientific view of Mars during the first billion years of its existence in our 4.56 billion year old Solar System. This strange shift is thought to have occurred at a time when life may have first emerged out of a primeval soup of non-living substances. It also provides an answer to three questions: why the Martian rivers formed where they are seen today; why underground reservoirs of water ice, until now thought to be anomalous, are situated so far from the poles of Mars; and why the Tharsis dome is located on the Martian equator. These new findings are published in the March 2, 2016 issue of the journal Nature by a team mainly composed of French planetary scientists.
Mars hasn’t always looked the way it does today. The Red Planet experienced its great tilt very long ago. The new research is the result of the combined work of geophysicists, geomorphologists, and climatologists, and according to this study, it was not the rotation axis of Mars that shifted–in a process termed a variation of obliquity–but instead it was the mantle and crust that rotated with respect to the inner core of the planet. In order to visualize this, imagine turning the flesh of a plum around on its stone. This phenomenon had already been predicted by theorists–however it had never before been demonstrated. The erupting Tharsis volcanic dome, which according to the new model caused the great Martian tilt, first began to take its incredible, enormous form over 3.7 billion years ago. Volcanic eruptions continued to occur for millions of years, and this activity formed a plateau that exceeds 5,000 kilometers in diameter, with a thickness of approximately 12 kilometers and a mass of a billion billion tons–which is about 1/70th the mass of Earth’s large Moon. This hefty mass was so huge that it made the crust and mantle of the Red Planet swivel around. Because of this, the Tharsis dome traveled to the equator, corresponding to its new equilibrium position.
Before this incredible tilt occurred, the Martian poles were not where they are now. In 2010, Dr. Isamu Matsuyama of the University of Arizona, Tucson, had already developed a geophysical model that showed that, if the Tharsis dome is eliminated from the Martian surface, the planet shows a different orientation with respect to its axis. According to this new study, geomorphologists Dr. Sylvain Bouley of the Universite Paris-Sud and Dr. David Baratoux of the Universite Toulouse III-Sabatier, both in France, show for the first time that the rivers on ancient Mars were originally situated along a south tropical band that rotated around poles that shifted by about 20 degrees with respect to their positions today. These poles are consistent with those calculated independently by Dr. Matsuyama. This correlation is supported by observations made by other scientific teams who had already observed signs of glacier melting and retreat, as well as evidence for the existence of subsurface ice, in what was once Martian polar regions.
Unveiling The Mysteries Of The Red Planet
Since the year 2000, cameras in orbit around the Red Planet have dispatched a treasure chest of revealing images back to Earth. These images have unveiled a Martian surface etched with small valleys that have been carved into slopes, and are hauntingly similar in shape to gullies formed by gushing water flowing on Earth. The Martian gullies are thought to be less than a few million years old–a mere blink of the eye on geological time scales. Indeed, some of the gullies appear to be much younger than that! These observations hinted to planetary scientists that large amounts of liquid water may still be present on the Red Planet today–and that this flowing water might be responsible for carving the gullies.
However, this particular model has been questioned as a result of frequent monitoring of the surface of this world by the HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter (MRO). Indeed, more recent observations reveal that the formation of the Martian gullies is still ongoing today, occurring during seasons when the surface environment of the Red Planet is too frigid for liquid water to flow. Conversely, the observed gully activity seems to occur when CO2 ice (dry ice)–which is condensed from the Red Planet’s atmosphere during its winter–is melting on the warming surface of Earth’s neighboring world.
Mars is often referred to as the “Red Planet” because of the large amount of iron oxide on its surface, which provides its reddish tint. This Earth-like, rocky world sports only a very thin atmosphere, and it reveals numerous surface features that resemble impact craters seen on the surface of Earth’s Moon, as well as valleys, deserts, polar ice caps, and volcanoes on our own planet. The Martian rotational period, and its changing seasons, are also hauntingly similar to those of Earth.
Unlike Earth’s own large, magnificent lunar companion, Mars possesses a duo of misshapen, very tiny moons named Phobos and Deimos. These tiny, fascinating potato-shaped moons are thought to have been born in the Main Asteroid Belt, situated between the orbits of Mars and the gas-giant behemoth of our Sun’s family, the enormous planet, Jupiter. It is thought that the tiny rocky duo probably escaped from the Main Asteroid Belt, and then wandered far from their birthplace, only to be captured by the powerful gravitational tug of Mars.
Mariner 4 succeeded in making the first successful flyby of Mars in 1965. This early visit of half a century ago triggered a great deal of speculation among planetary scientists that there may have existed life-sustaining liquid water on the Martian surface. This theory was devised on the basis of observed periodic alterations of dark and light areas, especially in the polar latitudes on Mars, which looked like irrigation channels for flowing liquid water. However, these intriguing straight lines were eventually determined to be mere optical illusions. Nevertheless, geological evidence continued to suggest to the scientists that once–very long ago–Mars was covered by large amounts of liquid water. In 2005, radar data showed that a large quantity of water ice existed on the poles of the Red Planet, as well as at mid-latitudes. In 2007, the Mars rover Spirit spotted chemical compounds containing water molecules, and the Phoenix lander directly detected the presence of water ice lurking in shallow soil samples on July 31, 2008.
At present, Mars is being visited by seven spacecraft, five of which are in orbit: 2001 Mars Odyssey, Mars Express, MRO, MAVEN, and Mars Orbiter Mission. The two missions that are currently roaming around and exploring the Red Planet’s surface are the Mars Exploration Rover Opportunity and the Mars Science Laboratory.
A New Face For Mars
Mars looked very different before its surface experienced the ancient, catastrophic shifting that caused a sea-change in its appearance. The Martian topography was recalculated by Dr. Matsuyama, in his study of the effects of this shifting on the surface of ancient Mars. Dr. Matsuyama’s research resulted in an alteration of a widely accepted scenario that suggests the Tharsis dome was almost completely formed before 3.7 billion years ago. According to this model, the Tharsis dome would have already existed before the Martian rivers formed, because it is responsible for controlling their flow direction. Based on the newly calculated topography, Dr. Bouley, Dr. Antoine Sejourne (Universite Paris-Sud), and Dr. Francois Costard of the French Centre National de la Recherche Scientifique (CNRS) demonstrated that despite the different relief, in the presence or absence of Tharsis, in both scenarios most of the rivers would have rushed away from the heavily cratered southern hemisphere highlands, and down to the low plains of the northern hemisphere. This research indicates that the rivers could have been altogether contemporaneous with the formation of the Tharsis dome.
The ancient Martian topography, before the great tilt, can also be used by planetary scientists to study the early climate of the Red Planet. Using climate models at the Laboratoire de Meteorologie Dynamique (CNRS), Dr. Francois Forget and Dr. Martin Turbet of the Institut de Phamacologie Moleculaire et Cellulaire (UPMC) in France, demonstrated that, with a frigid climate and an atmosphere much denser than it is today, ice accumulated at and around latitude 25 degrees South in Martian regions corresponding to the sources of what are now dried river beds.
This study is important because it proposes an alteration of our scientific perception of the ancient Martian surface–the way it was 4 billion years ago. In addition, it suggests the possibility of a significant alteration of the chronology of important events in primordial Martian history. According to this new model, the era of liquid water stability that permitted the formation of river valleys is contemporaneous with, and probably a result of, the intense volcanic eruptive activity of the powerful Tharsis dome. This new study suggests that the great tilt, triggered by immense and catastrophic eruptions of the Tharsis volcano, occurred after fluvial activity came to an end about 3.5 billion years ago–providing Mars with the new face that it displays today. This study proposes that this new view of Martian geography will have to be taken into consideration when scientists study primordial Mars during their hunt for large amounts of liquid water–and for traces of life.
