Monday, August 31, 2009


Twenty-two years ago, the Suizhou meteorite broke into 12 pieces and struck the ground near Hubei, China. This meteorite contained a high-pressure chromite-spinel polymorph called xieite, which was recently classified as the first new mineral with a post-spinel structure. The formation of this mineral requires temperatures between 1800 and 1950 °C, and pressures between 18 and 23 GPa. Because of the high temperatures and pressures required to form this mineral, it is believed that this meteorite suffered from a catastrophic collision.

The discovery of xieite was made by an American-Chinese team from the Guangzhou Institute of Geochemistry, Carnegie Institute of Washington, Chinese Academy of Sciences and the Geophysical Laboratory. Xieite was given official mineral status by the International Mineralogical Association’s Commission of New Minerals, Nomenclature and Classification. To be classified as a mineral, a substance must fit into five characterizations: 1) A mineral must be naturally occurring on Earth or somewhere in the Universe, not in a lab; 2) A mineral must be stable at room temperature (with the exception of ice and mercury); 3) A mineral should be inorganic, meaning it contains no C-C double bonds; 4) A mineral must be describable by a chemical formula-- in xieite’s case it is Fe2+ Cr2 O4; and 5) A mineral must have an ordered atomic arrangement.

Spinels are a class of isometric minerals with the general formula XY2O4. These minerals are found in the Earth’s upper mantle, starting at the core mantle boundary, or Mohorovicic discontinuity, and down to depths of about 70 km. Any spinel found at greater depths contain high amounts of chromite. If found in the Earth, post-spinel chromite (which is 10% more dense than spinel-chromite) would have to have formed deep in the mantle, at depths of about 500km.

Because of the high temperatures and pressures required for the formation of xieite, this new mineral could potentially become a useful tool for astronomers and geophysicists. If xieite is found in other asteroids, astronomers can use it to estimate the pressures and forces that have acted on the asteroid during impact. Likewise, if xieite is found in basaltic lava flows, or igneous intrusions, geophysicists can use the mineral to determine what depths in the mantle the magma originated.

Tuesday, August 25, 2009


Can life exist in the harsh conditions of our solar system? Could life evolve and survive under the extreme heat and pressure of Venus, under the icy crust of Mars, or in the oceans of Europa? To find out just how resilient life is, scientists have been looking for answers in some of the most hostile environments on Earth. And in recent years, life has been discovered in the most extreme conditions, previously thought to be uninhabitable. These microorganisms are sometimes called extremophiles.

There are many different classes of extremophiles, which are named according to the environmental conditions in which they thrive. For example, a thermophile is an organism which lives in conditions between 60˚ and 80˚ Celsius. Recently, a thermophile was discovered nearly two miles beneath the Earth’s surface in the Mponeng Gold mine of South Africa. This particular discovery is interesting because these thermophiles are completely devoid of sunlight, surviving on the byproducts of radioactive decay.

Where might we look for extremophiles outside of Earth? Mars is a good place to start. With the recent confirmation of ice in the crust, it is possible that water has trickled deep into the Martian interior, where thermophiles can survive off of radioactive materials like previously discussed. On Earth, we have discovered halophiles, which require high amounts of salt to survive; recently, the Phoenix Lander discovered several different types of salts in the Martian soil, which could be another location to search for life. Other types of extremophiles discovered on Earth may also apply to Mars, such as: xerophiles, hypoliths, and radioresistant extremophiles.

Europa is another great place to look for extremophiles. It is theorized that there is a global ocean beneath Europa’s thick layer of surface ice. Sattelite images of Europa’s surface show a complex system of tectonic activity–places where the ice has broken and liquid water has upwelled to the surface and refrozen. This tectonic activity is likely the result of tidal flexing, due to the gravitational pull of Jupiter. This tidal flexing may also produce hydrothermal vents. Earth’s hydrothermal vents are host to a large amount of biological activity, meaning Europa is a very promising place to look for extremophiles.

There are future plans in the works to search for extremophiles in the Martian crust. Astrobiological missions to Europa, Titan, or elsewhere are probably deep into the future. Given the amount of life discovered in the harshest places on Earth, I will be surprised if we find that our solar system is devoid of life.

Thursday, August 20, 2009


Saturn’s largest moon (the solar system’s second largest moon), Titan, was discovered in 1655 by Dutch astronomer Christiaan Huygens. In 1944, Gerard Kuiper demonstrated that Titan’s dense atmosphere has the spectral signature of methane. Up until the arrival of the voyager 1 in 1980 and Cassini-Huygens in 2004, Titan was somewhat of a mystery with its surface features hidden beneath thick layers of clouds and haze.

Although the surface was still hidden, Voyager was able to learn much about the moon’s planet-like atmosphere. Titan’s huge atmosphere creates a surface pressure of 1.5 bars, a temperature of 94K, and a density of 5.3kg/m3. This surface temperature is close to the triple point of methane, which could mean that Titan has a methane cycle similar to Earth’s hydrological cycle.

In 2005, ESA’s Huygens Probe was released from Cassini and entered Titan’s atmosphere. It discovered that Titan and Earth’s atmosphere share a similar altitude/temperature relationship. On Earth, the temperature decreases with altitude in the troposphere, increases in the stratosphere due to the absorption of UV rays in the ozone, decreases in the mesosphere due to decreasing atmospheric density, and finally increases in the thermosphere due to the release of thermal energy caused by the breakup of molecules by solar radiation. On Titan, the temperature decreases with altitude in the troposphere, and increases in the stratosphere.

With several Cassini flybys, Titan’s mysterious surface is finally being revealed. Titan’s surface is incredibly Earth-like with rain-cut river beds, hydrocarbon lakes, and giant equatorial sand dunes. Much is still unknown about the surface, such as the depth of the lakes, and how the sand dunes are formed. Cassini Radar observations also confirmed that the entire crust of Titan is floating on top of a massive water ocean.

On April 2008 a large storm cell, approximately the size of India, was observed using the combined technologies of several observatories, such as NASA’S Infrared Telescope located on Mauna Kea in Hawaii. This storm was observed over a tropical region which would be a typical place for tropical storms to develop. More recently, a second large storm system was observed over a more arid region, where such storms are less expected to develop. These storms could be capable of producing large amounts of precipitation which would sculpt the moon’s surface, creating the surface geology which we are just beginning to see.

With a continuing Cassini mission, including 20 plus Titan fly-bys, there is definitely more discoveries to come. Titan is a moon well worth exploring with complex orbiters and robotic landers, not only for further observations of Titan’s exotic surface features, but also to look for signs of extremophiles. Any such mission will be expensive and several years into the future, so in the meantime we can enjoy the only sounds ever recorded on a body other than Earth. These sounds were recorded by the Huygens Probe as it descended through Titan’s atmosphere: Sounds of Titan�

Wednesday, August 19, 2009

Going Up?

Imagine a 100,000 km elevator ride with the gentle beats of muzak slowly infiltrating your mind, while simultaneously your nostrils are attacked by the pungent scent of cheap perfume and the body odor of your fellow passengers. Some people might consider this to be torture, but chances are the assaults on the other four senses will be blocked out by the visual delight of the Earth slowly shrinking into a magnificent blue sphere; a view which is currently only experienced by a select few.

The idea of an elevator into space is not new. Konstantin Tsiolkovsky was the first to publish the idea in his 1895 paper: “Day-Dreams of Heaven and Earth”. It has also appeared in several Science fiction novels by authors such as Arthur C. Clarke. In a relatively short period of time, this idea has gone from an impossible dream to something that the Lift Port Group believes could happen within 23 years.

To reduce climate risks the elevator will be located somewhere along the equator, where it will climb a 100,000 km ribbon to a space station which will act as a counterweight. This ribbon is the main technological hurdle which needs to be surpassed in order achieve this dream. Carbon nanotubes appear to be the answer and experts say that the technology to build strong enough fibers may be reached in the next couple years.

An elevator to space would have many benefits. An estimated cost of delivering cargo to orbit is only $100/lb compared to current costs of up to $60,000/lb. The savings in cost would improve exploration as more money could be spent on instruments. An elevator to space would ultimately open the doors to space tourism, mining and any number of other entrepreneurial adventures.

If the technological requirements are met, will financial and legal issues prevent the timely construction of one of mankind’s greatest dreams? Or could my generation be riding an elevator to our low-gravity retirement homes?

Monday, August 17, 2009

Could Saturn's Moon Enceladus Harbor Life?

Saturn’s sixth largest moon, Enceladus, was discovered in 1789 by British Astronomer William Herschel. With a low albedo and close proximity to Saturn, Enceladus is difficult to observe. Because of this difficulty little was known about this moon until the Voyager flybys in the 1980’s. Voyager 1 discovered that Enceladus is located in the densest part of Saturn’s E Ring, and Voyager 2 discovered that Enceladus has diverse and relatively complicated surface features.

In 2005 Cassini discovered that Enceladus is the fourth known body in the solar system with active volcanism. The other three are Earth, Jupiter’s moon Io, and Neptune’s moon Triton. This volcanism causes icy jets, plumes of water vapor, and other materials to be shot into the atmosphere. It is this cryovolcanism which was determined to be the cause of Saturn’s E Ring. Just recently Cassini photographed the volcanic southern pole. These pictures revealed a geological feature which scientists are calling “tiger stripes”. These tiger stripes are 300 meter deep fractures and are surrounded by chunks of ice, and are the source of Enceladus’s

During a recent flyby, Cassini was able to detect ammonia within these icy plumes. This ammonia would allow water to remain in its liquid phase at lower temperatures than are normally allowed under the moons temperatures and pressures.

Cassini also discovered the cause of the tectonic activity. Enceladus, like many other moons is traped in orbital resonances, this causes tidal heating on the moons interior. Like thought to exist on Jupiter’s moon Europa, this could also cause Enceladus to have a subsurface liquid ocean. Because of the volcanic activity a subsurface ocean on Enceladus is thought to be only tens of meters beneath the surface, where the oceans on Europa are thought to be 100 kilometers beneath the surface.

Does Enceladus have a subsurface ocean? If it does, is this another place to look for signs of life? The moons ability to retain liquid water at lower than normal temperatures, and the discovery of organic materials within icy the plumes suggests that Enceladus could be one place worth searching for extraterrestrial extremophiles.

Sunday, August 16, 2009

The Kepler Mission

Since the dawn of intelligent man, we as a race have asked several questions pertaining to the heavens, and to the meaning of life. In 2012, NASA’S Kepler Mission will bring us one step closer to answering one of these timeless questions: “are we alone?” Launched in March of this year, the Kepler Mission was not only named after the great mathematician and astronomer, Johannes Kepler, it also celebrates the 400th anniversary of the publication of his first two laws on planetary motion.

The Kepler spacecraft will search for Earth-like planets using a technique known as the Transit Method of Detecting Extrasolar Planets. A transit occurs when a planet crosses in front of its host star as viewed by an observer. These transits dim the brightness of a star which allow for the detection of extrasolar planets. This change in brightness is very difficult to detect by terrestrial planets, such as Earth, because they only dim their host star by 100 parts per million, lasting only 2 to 16 hours. In order for an extrasolar transit to be observed from our solar system, the orbit must be viewed edge on. The probability of observing such a planet is less than 1%. To increase the chances of observing a transiting terrestrial planet, the Kepler spacecraft will observe 100,000 of our neighboring stars. Because any planet in the habitable zone will require an orbit close to that of one Earth year, Kepler will need to observe any transits discovered amongst these 100,000 stars for at least 3.5 years to determine if the transit is periodic enough to be a planet.

The precision of the spacecraft was recently tested by observing a known exoplanet called HAT-P-7. This planet orbits a star 1000 light years away in approximately 2.2 days. Not only was Kepler able to observe transit with the precision necessary for the detection of an Earth sized planet, the light given off by this planet was also observed. This is the first time light from an exosolar planet has been observed, this light can provide information about the planet’s atmosphere.

The Kepler Mission may not be able to directly determine whether or not we are alone in the universe, but it will be able to tell us if we have neighboring planetary systems, containing planets, capable of sustaining life. When compared to all the stars in the universe, even one discovery amongst the relatively small sample space of 100,000 stars will be significant enough for us to rethink our meaning and place in the universe.