In 2005 Saturn’s moon Enceladus was discovered to be an active world with water ice particle geysers at its south pole. The driver of this activity on a moon so small remains a mystery. One possible explanation has been suggested by Dr. Francis Nimmo, a planetary scientist from the University of California Santa Cruz. Nimmo visited the University of Arizona Lunar and Planetary Laboratory to present his model on Thursday, September 18, 2007 for the department’s weekly Planetary Sciences Colloquium. The talk was based on his recent publication [reprint PDF] “Shear heating as the origin of the plumes and heat flux on Enceladus” in Nature.

While the old view of the outer solar system as a cold and dead region devoid of most geological activity has eroded with surprising discoveries since the 1980’s, one bias persisted until 2005: only large moons in the outer solar system could potentially be active. Below a particular diameter, moons were not believed to be able to produce sufficient internal heating to drive surface activity. With a diameter of only 252 kilometers (157 miles), Enceladus was expected to have frozen solid long ago. The discover of geysers and a thin oxygen atmosphere at Enceladus proved that this was not the case.

Enceladus’ geysers do not appear to be a global phenomena, however. They are localized to the moon’s south pole, apparently along fractures referred to as “Tiger Stripes.” Taking into consideration the moon’s size, possible internal structures, orbital eccentricity, and other characteristics Nimmo has been working to develop a model that can explain the localized nature of this activity.

An important feature of his model is reorientation theory, where a mass such as a diapir rising to the surface from the mantle can reorient a body, driving the mass’ surface expression toward the poles or equator over time. The presence of such a mass would indicate some driving force such as convection. Applied to Enceladus, this could explain why the tiger stripes have reorientated to their present location at the south pole.

While this may explain the tectonic activity at the south pole, the presence of active water ice plumes requires further explanation. If the tiger stripes are strike-slip faults like the San Andreas Fault on the Earth, then rapid enough motion back and forth along the faults could lead to uplift and shear heating. This friction leads to sublimation of water ice, the primary component of the crust of Enceladus, with some of that vapor being released with heat along the tiger stripes in the form of the spectacular plumes photographed by the Cassini spacecraft.

After developing this model, which Nimmo believes is a better explanation than other theories that have been put forward, such as a near-surface ocean or clathrate decomposition, Nimmo and his colleagues explored possible predictions. While a near-surface ocean does not provide the water vapor to geysers in his model, the model still suggests the presence of an ocean underneath a solid ice crust of at least 5 kilometers (3 miles). The model suggests that this ocean may be transitory, with significant freezing out or remelting depending on the tidal dynamics that change as Enceladus’ orbit around Saturn changes over time.

Furthermore, the orientation of the tiger stripes should change over time, and their fault motions should result in hotter or colder relative temperatures depending on how fast they are moving. In the paper, the team of researchers specify two portions of stripes they predict will have the highest relative tempatures. Some researchers believe fossil tiger stripes may be present elsewhere on Enceladus. Further observations of Enceladus may allow them to test this prediction and confirm or deny the presence of fossil tiger stripes.

Nimmo acknowledged that at present this model of Enceladus is simplistic with several questions still outstanding. Why, for example, does heating appear only at the south pole and not also at the north pole, as predicted by some models of subsurface tidal heating? What prevents the ocean, if it exists, from freezing out completely? Enceladus remains a mystery and will continue to be an important study target for planetary scientists still marveling at a frigid but incredibly active outer solar system.

More Information

• Dr. Francis Nimmo at the University of California Santa Cruz
• Cassini-Huygens Website
  • Saturn’s Moons section
  • Enceladus Information

Image caption: X PRIZE Moon exhibit and logo at WIRED NextFest

A robotic scavenger hunt to the moon is the next big space competition. The X PRIZE Foundation announced at Wired NextFest, along with representatives from Google, NASA, and one of the Apollo 11 astronauts, the Google Lunar X PRIZE. The largest incentive competition in history, US$30 million will go to the first and second privately funded teams to land a rover on the Moon.

US$20 million will be awarded to the first team who makes a soft landing on the surface of the Moon, drives a least 500 meters, and takes two sets of high definition video and images. The second team to accomplish the same tasks will be awarded US$5 million. In addition, $5 million will be awarded for bonus tasks, including finding artifacts from past mission, finding water ice at the lunar south pole, surviving one full lunar night of frigid temperatures, and driving a total of 5 kilometers instead of 500 meters.

On hand for the announcement were Dr. Peter Diamandis, X Prize chairman Robert K. Weiss, Google co-founder Larry Page, Apollo 11 astronaut Buzz Aldrin, Space Exploration Technologies (SpaceX) founder Elon Musk, and NASA Deputy Administrator Shana Dale. Video messages from Google co-founder Sergey Brin and director James Cameron were shown. All expressed their support for the latest prize.

According to Page, science has a serious marketing problem. Competitions like the Google Lunar X PRIZE can help promote science and engineering, while continuing to push progress and economic growth. Page announced during his comments a new version of Google Moon with improved resolution and panoramas captured by Apollo.

Through video and speech, the X PRIZE Foundation recapped incentive competitions to date, including the 2004 culmination of the first X Prize for a private manned suborbital launch. Since then, several new prizes have been announced, including the Archon Genomics X PRIZE, Automotive X PRIZE, and upcoming educational, life science, and energy prizes. The latest prize is being marketed as “Moon 2.0″, with previous lunar activity through the final Apollo mission in 1972 referred to as Moon 1.0. While Moon 1.0 was a competition between the superpowers, Moon 2.0 is expected to open up the moon as a resource.

X PRIZE’s Weiss listed surface silicon and water ice as important lunar resources to enable manned missions of the Moon and potentially help with resource issues on the Earth, including energy concerns. Diamandis said the Google Lunar X PRIZE will be the first commercial steps to exploiting the resources of the Moon.

SpaceX’s Musk announced they will donate profits they would normally make on space launches to lower the cost of launch of X PRIZE competitors’ entries. Other organizations like SETI will provide services to competitors for reduced or no cost.

The setting for the announcement - Wired NextFest - allowed for a somewhat elaborate stage, including a remote controlled rover that joined Diamandis at one point, a life-sized model of an astronaut and lunar rover, and a huge model of the moon unveiled for the photo-op at the end of the presentations, with Diamandis exclaiming “Let the race begin!”. In additions to participating representatives and media, there were many students, parents, and teachers in attendance for the announcement.

A video dramatization of a private team winning the Google Lunar X PRIZE in the future included depictions of access to data returned by the mission via the Internet on laptops, iPhones, and video billboards. Currently, a new website - http://www.googlelunarxprize.org/ - has been created to host educational videos, tools, and hands-on activities for students.

Image caption: X PRIZE Moon and rover exhibit at the fourth annual WIRED NextFest

Image caption: X PRIZE exhibit of Apollo astronaut and moon rover at the fourth annual WIRED NextFest

Image Credit: NASA/JPL-Caltech/C. Martin (Caltech)/M. Seibert(OCIW) - “Johnny Appleseed of the Cosmos“

The first star discovered with a comet-like tail was announced today by the Galaxy Evolution Explorer (GALEX) team. While exploring the sky in ultraviolet light, GALEX spotted a tail of material streaming behind the binary star Mira, or Omicron Ceti, located 450 light year from the Earth. The red giant member of the binary, Mira A, appears to be ejecting material as it hurtles through the galaxy at 130 kilometers per second (291,000 miles per hour).

The tail visible today stretches nearly 13 light years long, representing an estimated 30,000 years of history. Scientists plan to study the tail to learn more about the evolution of red giants as well as how such tails form in the first place. The discovery came a surprise as such a phenomena had not been predicted before.

More Information

• Galaxy Evolution Explorer (GALEX)
  • Wednesday, August 15, 2007 Press Release: “SPEEDING BULLET STAR LEAVES ENORMOUS STREAK ACROSS SKY“
• Wikipedia: Mira

The HiRISE team has released more of the high resolution “test” images of Mars taken on March 23 and 25, 2006. Incredible detail, color, and a perspective view. Eight images were taken and the rest should be available tomorrow.

read more | digg story

Mars Reconnaissance Orbiter (MRO) performed a flawless engine burn today in a successful bid to enter orbit around Mars. The event, known as Mars Orbital Insertion (MOI), is a risky one for robotic visitors to the Red Planet. Now that MRO is safely in orbit, the spacecraft will soon begin several months of aerobraking to reshape the orbit into a circle approximately 300 km above the martian surface. The primary science phase of the mission will begin in the fall after aerobraking has been completed.

At the University of Arizona, an audience of students, the public, reporters, and other guests watched live NASA TV coverage of the event. The High Resolution Imaging Science Experiment (HiRISE) camera is one of the instruments on board MRO and is operated by a team at the University of Arizona. HiRISE Principal Investigator Alfred McEwen and operations team members were on hand for presentations, narration of the television coverage, and answers to audience questions. [Disclosure: Richard Leis is a HiRISE operations team member.]

The risks of any orbital insertion include missing the target altogether or coming in too closely. During MRO MOI, all predicted events occurred on schedule, including the loss of signal from the spacecraft while it passed behind Mars. Reacquisition of the signal from MRO occurred at around 3:15 pm Mountain Standard time, and a few minutes later flight operations at the Jet Propulsion Laboratory in Pasadena, California, USA confirmed that the spacecraft was in the correct initial orbit around Mars. The audience and HiRISE team applauded and cheered the successful conclusion of each major event.

MRO launched from Cape Canaveral in Florida, USA on August 12, 2005. During its 7 month cruise to Mars, instruments on board were turned on and tested in preparation for future science gathering. HiRISE, for example, snapped high resolution images of the moon and stellar clusters. These images are now being used by the operations team to calibration the instrument and develop imaging processing software and procedures.

MRO will remain in its current orbit for about two weeks prior to the start of aerobraking. During that two weeks, some of the operations teams for the various instruments will again turn on their instruments. HiRISE will take nine images of Mars and once again the operations team will use these images for further calibration and testing.

Aerobraking occurs when MRO dips down into the martian atmosphere to create friction that helps slow down the spacecraft and lower its orbit. The process will take from five to seven months depending on the condition of the martian atmosphere on any given day.

After aerobraking, MRO will into a transition orbit during which time the instrument teams will complete their preparations for the primary science phase of the mission. Know as PSP, this phase of the mission will last for two years while scientific data is gathered.

The HiRISE camera is the largest such device ever sent outside the Earth’s orbit. The camera will capture high resolution images of the martian surface, up to 20,000 by 60,000 pixels in size. These images are so huge that they will not fit full size on a regular computer monitor. Only a display array of 20 by 60 monitors would have enough pixels available to show one full-sized HiRISE image. Because of this, recent compression and delivery technology known as JPEG2000 is being used to allow the scientific community and the public to browse through these images over the internet.

At its best setting, HiRISE will be able to see objects roughly one meter (approximately one yard) in size. Meanwhile, two other cameras will take lower resolution images but provide more coverage of the planet. Together, these cameras should reveal a different Mars than shown by previous orbiters, simply because so much more detail and wider coverage will become available than ever before. In fact, so much data will be obtained during the course of the mission that it will dwarf what many previous missions have obtained, combined.

MRO is also equipped with a sounding radar called SHARAD (Shallow Radar) which will return the highest resolution data of the martian subsurface. In recent years, previous spacecraft have detected the presence of water deposits beneath the surface of Mars. SHARAD will attempt to better quantify the amount of water present and in what form – ice or liquid – it exists.

Scientists hope to learn where the water believed to have existed on early Mars went, in what form it exists today, and if water might still flow on the surface (as appears to be the case with gullies discovered by previous spacecraft.) They also hope to learn more about the martian atmosphere and surface history. The information obtained could help determine whether or not Mars has ever been hospitable to life and which locations are best to search for fossil or current lifeforms.

More Information

• Mars Reconnaissance Orbiter (MRO)
• The view from MRO.
• HiRISE
  • HiRISE Presentation (Powerpoint file)
  • Mars Mania II - Saturday, April 08, 2006 at the University of Arizona campus

The modern robotic investigation of comets began with a spacecraft from the European Space Agency (ESA) named Giotto. Giotto captured in 1986 the first close-up images of a cometary nucleus and a wealth of other data. ESA is marking the 20th anniversary of Giotto’s successful flyby of Comet Halley on the eve of a NASA press conference regarding science results from the Stardust mission. Twenty years after Giotto, our knowledge about comets, those cold remnants of our solar system’s formation, is undergoing a revolution.

By 1986, six spacecraft were ready for an unprecedented scientific investigation of Comet Halley as it returned to the inner solar system. Due to budget cuts, NASA’s ambitious plans to study Comet Halley were reduced to long distance observations using the International Sun-Earth Explorer 3 (ISEE-3) spacecraft (renamed Interplanetary Comet Explorer (ICE)) already in operations. Meanwhile, after flying by Venus, the Russian Space Research Institute (IKI) spacecrafts VEGA-1 and VEGA-2 were directed toward Comet Halley. Japan’s Institute of Space and Aeronautical Science, which in 2003 became part of Japan Aerospace Exploration Agency (JAXA), used their existing SAKIGAKE (MS-T5) spacecraft for long distance observations and launched SUISEI (PLANET-A), a spacecraft specifically built to study Comet Halley. ESA’s Giotto spacecraft rounded out “Halley Armada.”

Named after the painter of “Adoration of the Magi” which includes a representation of a comet widely believed to be based on Comet Halley, Giotti flew closer to the comet than any of the other spacecraft. The dramatic images and other data returned revealed that Halley was not a round and icy “snow ball” as expected but instead an irregular and dark “dirt ball.” Jets of ice and gas volatiles erupted from the sun-heated surface of the nucleus, creating the bright and extensive coma and tail visible from the Earth.

This first close-up look at a comet revolutionized our understanding of the objects. Since then, several other robotic missions have provided even more highly detailed images and data. Tomorrow, scientists will hold a press conference to report the first science results from their analysis of the first pristine cometary material returned to Earth for extensive analysis. What we learn from the Stardust mission will no doubt radically advance our knowledge.

In twenty years, from the first close-up images of a comet to the first cometary material returned for study, we have learned more about the formation of our solar system and perhaps even the history of life on Earth than in all the thousands of years of comet observation that preceded the Space Age. From Giotto to Stardust in the blink of an eye.

More Information

• ESA Press Release - “Giotto’s brief encounter“
• Halley Armada:
  • Interplanetary Comet Explorer (ICE)
  • SUISEI (PLANET-A)
  • SAKIGAKE (MS-T5)
  • VEGA-1 and VEGA-2
  • Giotto
• Stardust
  • Press Conference, Monday, March 13, 2006 - “NASA ANNOUNCES FIRST STARDUST COMET SAMPLE RESULTS” | Announcement | NASA TV

Cassini-Huygens mission scientists discovered last year that plumes of ice erupt from the surface of Saturn’s moon Enceladus, but the mechanism for the this process has not been fully explained. Now a review of competing theories and available data implicates the more unlikely source: pressurized liquid water pools or an ocean near the moon’s surface. How water can be liquid on an apparently frozen body in the cold of the distant solar system is just the latest mystery regarding Enceladus.

Several research papers regarding recent findings about Enceladus are available in the March 10, 2006 issue of Science. In a Research Article entitled “Cassini Observes the Active South Pole of Enceladus”, Dr. Carolyn Porco, Cassini imaging team leader at Space Science Institute in Boulder, Colorado, USA and other mission scientists suggest that “water vapor probably venting from subsurface reservoirs of liquid water” provides the source for the majestic surface plumes discovered last year. In turn, these plumes may continually replenish Saturn’s E-ring.

Enceladus become just the fourth object in the solar system suspected of containing liquid water reservoirs because of tantalizing new evidence. Only Earth is known for certain to have liquid water on and below its surface. Evidence for liquid water aquifers on Mars and an ocean deep beneath the ice on Jupiter’s moon Europa have already led to excitement within the scientific community over the past decade. Now that Enceladus has been added to list, the mystery of processes that lead to liquid water only deepens.

If pools or oceans of liquid water exist on Enceladus, where do they come from? A heating source is required to raise the temperature to above 273 degrees Kelvin (0 degrees Celsius.) Mission scientists suspect flexing of the moon caused by its orbit around Saturn or a gravitational tug-of-war between Titan and Saturn, along with radioactive decay within the moon’s interior lead to heating that locally heats crustal water ice. Under pressure, this liquid water eventually escapes to the surface as geysers near the moon’s south pole.

The region near Enceladus’ south pole is striking for its so-called Tiger Stripes, enormous gashes across the surface that a significantly more warm than the surrounding terrain. The lack of craters and the apparent youth of ice in the area all suggest recent resurfacing. The discovery of the ice plumes confirmed this observation.

Mission scientists will continue to sift through the data returned by Cassini to investigate Enceladus. Cassini is currently scheduled to return for a close flyby of Enceladus on Wednesday, March 12, 2008 after a mission focus on Titan over the next two years has concluded.

More Information

• Cassini-Huygens Website
  • NASA/JPL News Release, March 09, 2006 - “NASA’s Cassini Discovers Potential Liquid Water on Enceladus“
  • Saturn’s Moons section
  • Enceladus Information

Mars Reconnaissance Orbiter (MRO) is scheduled for Mars Orbital Insertion (MOI) on Friday, March 10, 2009. Confirmation of success should arrive around 3:15 pm MST. Below is a link to a presentation I gave one of my classes today about the High Resolution Imaging Science Experiment (HiRISE) on board MRO, the highest resolution camera every sent on a planetary science mission. [Disclosure: Richard Leis is a HiRISE operations team member.] All of the spacecraft primary science mission cameras are shut down and will not be turned on until after orbital capture, but I have also included a link to a webpage that updates every 5 minutes a simulation of how Mars would look if you were riding along on MRO. Mars is getting close!

• HiRISE Presentation(Powerpoint file) attached to this article
• The view from MRO.

Astronomers from the European Southern Observatory (ESO) announced today the discovery of an exoplanet only 5.5 times the mass of the Earth orbiting a red dwarf star located near the center of the Milky Way galaxy, some 20,000 light years away from our own solar system. The discovery could indicate that rocky planets like the Earth are common throughout the universe.

The discovery of the exoplanet is only the third using a technique called gravitational microlensing. Microlensing is a faint but detectable brightening of light from a more distant object caused by gravitational lensing by a nearer object passing directly in front of it as seen from the Earth. Microlensing does not provide a direct visual observation of intervening bodies but instead indicates their presence indirectly.

A network of robotic telescopes monitors the galaxy 24 hours a day, 7 days a week, looking for microlensing events. Using the Danish 1.54m telescope at ESO La Silla, Chile, astronomers detected a microlensing event on July 11, 2005 by an intervening star less massive than our own Sun. Immediately after the event was detected, notification went out across the network to provide constant coverage of the phenomena. Ten days later, an anomaly in the wanning microlensing effect indicated the presence of a planet.

The planet has been labeled OGLE-2005-BLG-390Lb after the designation for the microlensing event. Astronomers speculate that the planet is cold and probably contains a significant amount of ice in its composition due to its location approximately three times as far from its parent star as the Earth is from the Sun. Its size is sufficient to hold a substantial atmosphere but such an environment may not be hospitable to life as we know it.

According to NASA’s “Planet Quest” site, 159 exoplanets have been detected to date, although other sources give a number closer to 170. Only one other rocky exoplanet candidate has been discovered and only one exoplanet has been directly imaged. Space agencies and astronomers are developing improved telescopes, spacecraft, and techniques to accelerate the detection and direct imaging of Earth-sized exoplanets over the next decade. The improved technologies may also allow scientists to look for evidence of biological markers in the atmospheres of exoplanets to determine the extent of life in our galaxy.

More Information

• Scientific Paper: Nature Letter, J.-P. Beaulieu, et. al., “Discovery of a cool planet of 5.5 Earth masses through gravitational microlensing“, Nature 439, 437-440 (26 January 2006) | doi:10.1038/nature04441
• European Southern Observatory (ESO)
  • Press Release – January 25, 2006 – “It’s Far, It’s Small, It’s Cool: It’s an Icy Exoplanet!“
  • Video: ESO PR Video 03a/06
• United States National Science Foundation
  • Press Release - January 25, 2006 - “Closer to Home“
  • Images and Video
• Technology - Microlensing events are rare and last only a short time (generally days.) Therefore, networks of robotic telescopes have been set up to automate observation and provide continuous coverage during an event.
  • Probing Lensing Anomalies NETwork (PLANET)
  • RoboNet-1.0
  • The Optical Gravitational Lensing Experiment (OGLE)
  • Microlensing Observations in Astrophysics (MOA)
• Planet Quest - the search for another Earth

The United States Geological Survey (USGS) National Earthquake Center has unveiled upgraded technology, 24/7 staffing, and a new website to be rolled out over the next few months in response to the 2004 Indian Ocean tsunami and a wider call for better earthquake monitoring. The effort includes HYDRA, a system that will provide more detailed information about earthquakes and their potential for damage based on the region affected. HYDRA is expected to be completed in March 2006.

By providing staffing for operations around the clock, the USGS hopes to provide more timely information about earthquakes soon after they occur. The existing website, located at http://earthquake.usgs.gov, already provides maps, news and an RSS feed about recently detected earthquakes from around the world. A redesign set to debut at the end of January 2006 will enhance the site with information from the new monitoring system.

Emergency appropriations and congressional funding for the effort came last year after the magnitude 9.0 Sumatra Earthquake and tsunami that followed killed nearly 300,000 people on December 26, 2004 in one of the worst natural disasters in recent history. Experts believe that monitoring equipment in the Indian Ocean and improved notification technology could have helped prevent many of these deaths. Although the USGS detected the earthquake immediately after it occurred, they were unable to track down the appropriate authorities in countries in the affected region. Earthquake monitoring equipment and notification already exist for the Atlantic and Pacific oceans.

Earthquakes occur at boundaries where the plates that make up the Earth’s lithosphere and crust collide with, separate from or scrape past each other, as well as localized areas of instability caused by volcanic activity, faulting, and other phenomena. In the United States, 39 states are considered to be at some significant risk of earthquakes. The increasing number of people who live in earthquake prone regions will require continued improvements in current monitoring and notification technologies.

More Information

• USGS Earthquake Hazards Program
  • 01/19/2006 USGS Press Release - “USGS National Earthquake Center goes 24/7 — Staff now on-site night and day to locate and report worldwide quakes“