Although somewhat blobby and deformed, this is in fact a spiral galaxy, located in the southern constellation Hydra. Imaged by Hubble as part of a survey of galactic bulges, NGC 4980 exhibits what’s called a “pseudobulge” — an inline central concentration of stars whose similar spiral motion extends right down into its core.
As opposed to classical bulges, in which stars orbit their galaxy’s core in all directions, pseudobulges are made up of stars that continue along the spiral motion of the galactic arms all the way into the center. Pseudobulges are typically seen to contain stars that are the same age as most of the others in the galaxy.
In contrast, classical bulges usually contain stars older than those found in the disk, leading astrophysicists to believe that galaxies with classical bulges had undergone one or more collisions with other galaxies during their evolution.
Our own Milky Way is thought to have a pseudobulge, while some spiral galaxies have no discernible bulge at all.
This image is composed of exposures taken in visible and infrared light by Hubble’s Advanced Camera for Surveys. The image is approximately 3.3 by 1.5 arcminutes in size. NGC 4980 is located about 80 million light-years from Earth.
After NASA was forced to back out the joint ExoMars mission with the European Space Agency due to budget constraints, ESA went looking for help with the planned multi-vehicle Mars mission. Now, reportedly the Head of Roscosmos Vladimir Popovkin met with Director General of the ESA, Jean-Jacques Dordain last week, and the two signed a memorandum of understanding to work together to make ExoMars a reality.
“The sides consider this project feasible and promising,” Popovkin’s spokeswoman Anna Vedishcheva was quoted in Ria Novosti. “The sides are to sign the deal by year-end.”
Russia’s participation in the project was also approved by the space council of the Russian Academy of Sciences.
The ExoMars program was slated to send an orbiter to Mars in 2016 and a rover in 2018, but after NASA pulled out of its part of the bargain — of providing several science instruments and an Atlas launch vehicle – ESA knew they could not do the entire mission on their own. Last fall, when it was becoming apparent that NASA’s ability to participate was in jeopardy, Dordain extended an invitation to Russia, and in turn Roscosmos officials hinted they might be interested in joining, offering to provide the use of their Proton rockets for the launches. The two space agencies then had preliminary talks at the Ariane 5 launch at Kourou, French Guiana in March, 2012.
Russian space agency chief Vladimir Popovkin said that Russia’s financing of ExoMars could be partially covered by insurance payments of 1.2 billion rubles (about $40.7 million) for the lost Phobos-Grunt sample return mission that would have gone to the Martian moon Phobos.
The details of the new ExoMars partnership are yet to be worked out, but the ESA/NASA partnership would have sent the Trace Gas Orbiter to the Red Planet in 2016 to search for atmospheric methane — a potential signature for microbial life – as well as an advanced astrobiology rover to drill into the surface in 2018, with the hopes of determining if life ever evolved on Mars.
Unsurprisingly, the potential deal with Russia comes as a huge relief to European space scientists who have spent years working on ExoMars. Journalist Paul Sutherland quoted UK scientist John Zarnecki of the Open University, as saying, “It looks like the cavalry has come riding over the horizon to save us, but this time they are dressed in Russian uniforms. There will be a lot scientists in universities and research institutes throughout Europe who will be very relieved to hear this news. Otherwise it seemed that several years work preparing instruments for this mission was going to go down the drain.”
Recent images from ESA’s Mars Express spacecraft reveal long rows of crater-like depressions lining the flanks of ancient Martian volcanoes located in the planet’s vast Tharsis region. Rather than being the result of impact events, these “pit chains” were likely caused by underground lava flows — and could be a prime location for look for life.
Like similar features found on Earth, lava tubes on Mars are the result of rivers of magma that carved channels beneath the surface. When these channels empty out, a hollow tube is left. If the roof of a particularly large tube is near the surface the roof can eventually collapse, creating a surface depression… or, in some cases, opening up to the surface entirely.
Even though volcanism on Mars isn’t currently active — the last eruptions probably took place at least over a million years ago — the features left by volcanic activity are still very much present today and likely well-preserved beneath the Martian surface.
Shielded from harsh solar and cosmic radiation, the interior of such lava tubes could provide a safe haven for microbial life — especially if groundwater had found its way inside at some point.
Even though the surface of Mars can receive 250 times the radiation levels found on Earth, the layers of soil and rock surrounding the tubes can provide adequate protection for life, whether it be ancient Martian microbes or future explorers from Earth.
Of course, water and protection from radiation aren’t the only factors necessary for life. There also needs to be some source of heat. Fortunately, the pit chains imaged by Mars Express happen to be within one of the most volcano-laden areas of the Red Planet, a region called the Arcadia quadrangle. Within this area exist some of the largest volcanoes on Mars — and the Tractus Catena pits are located right in the middle of them.
If a heat source were ever to have been beneath the surface of Mars, there would be a good chance it would have been here.
And if our own planet is any measure of such things, where there’s heat and water there is often some form of life — however extreme the conditions may be.
“I’d like to see us land ON a volcano,” Dr. Tracy Gregg, a volcanologist with the University of Buffalo, had once told Universe Today back in 2004. “Right on the flanks. Often the best place to look for evidence of life on any planet is near volcanoes.”
“That may sound counterintuitive, but think about Yellowstone National Park , which really is nothing but a huge volcano,” Gregg elaborated. “Even when the weather in Wyoming is 20 below zero, all the geysers, which are fed by volcanic heat, are swarming with bacteria and all kinds of happy little things cruising around in the water. So, since we think that the necessary ingredients for life on Earth were water and heat, we are looking for the same things on Mars.”
As far as any remaining geothermal activity still happening beneath the Martian surface?
“I strongly suspect there are still molten (or at least mushy) magma bodies beneath the huge Tharsis volcanoes,” Gregg had said. (Read the full article here.)
On Earth, lava tubes, caves and underground spaces of all kinds harbor life, often specialized forms that are found no place else. Could this be (or have once been) the case on Mars as well? Only future exploration will tell. Until then, places like Tractus Catena will remain on scientists’ short list of places to look.
First discovered by Charles Messier in 1764, the globular cluster Messier 9 is a vast swarm of ancient stars located 25,000 light-years away, close to the center of the galaxy. Too distant to be seen with the naked eye, the cluster’s innermost stars have never been individually resolved… until now.
This image from the Hubble Space Telescope is the most detailed view yet into Messier 9, capturing details of over 250,000 stars within it. Stars’ shape, size and color can be determined — giving astronomers more clues as to what the cluster’s stars are made of. (Download a large 10 mb JPEG file here.)
Hot blue stars as well as cooler red stars can be seen in Messier 9, along with more Sun-like yellow stars.
Unlike our Sun, however, Messier 9’s stars are nearly ten billion years old — twice the Sun’s age — and are made up of much less heavy elements.
Since heavy elements (such as carbon, oxygen and iron) are formed inside the cores of stars and dispersed into the galaxy when the stars eventually go supernova, stars that formed early on were birthed from clouds of material that weren’t yet rich in such elements.
Zoom into the Messier 9 cluster with a video from NASA and the European Space Agency below:
The Hubble Space Telescope is a project of international cooperation between ESA and NASA. See more at www.spacetelescope.org.
Image credit: NASA & ESA. Video: NASA, ESA, Digitized Sky Survey 2, N. Risinger (skysurvey.org)
The heaviest cargo ship ever has arrived and docked to the International Space Station, laden with 7 tons of supplies for the 6-member ISS crew. The 20-ton European ATV-3 cargo ship, named “Edoardo Amaldi” after the Italian physicist and spaceflight pioneer, made a “smooth and gentle” docking on March 28, 2012, the European Space Agency said. The supplies delivered included food, drinking water, clothing, oxygen, spare parts and fuel.
The ATV launched from Kourou, French Guiana last Friday. It will use its engines to boost the space station during its 5-month stay on orbit. It is scheduled to undock on August 27 and perform an “orbital cremation” of trash from the space station.
Just days after President Obama met with brilliant High School students at the 2012 White House Science Fair to celebrate their winning achievements and encourage America’s Youth to study science and take up careers in the Science, Technology, Engineering and Math (STEM) technical fields, the Obama Administration has decided on deep budgets cuts slashing away the very NASA science programs that would inspire those same students to shoot for the Stars and Beyond and answer the question – Are We Alone ?
Last year, the Obama Administration killed Project Constellation, NASA’s Human Spaceflight program to return American astronauts to the Moon. This year, the President has killed NASA’s ExoMars Robotic Spaceflight program aimed at dispatching two ambitious missions to Mars in 2016 and 2018 to search for signs of life.
Both ExoMars probes involved a joint new collaboration with the European Space Agency (ESA) carefully crafted to share costs in hard times and get the most bang for the buck – outlined in my earlier Universe Today story, here.
Expert Scientists and Policy makers have been voicing their opinions.
All of NASA’s “Flagship” Planetary Science missions have now been cancelled in the 2013 Fiscal Year Budget proposed on Feb. 13, and others missions have also been curtailed due to the severe economy.
“There is no room in the current budget proposal from the President for new Flagship missions anywhere,” said John Grunsfeld, NASA’s Associate Administrator for Science at a NASA budget briefing for the media on Feb. 13.
ESA is now looking to partner with Russia as all American participation in ExoMars is erased due to NASA’ s forced pull out.
On Feb. 13, NASA’s Fiscal 2013 Budget was announced and the Obama Administration carved away nearly half the Mars mission budget. Altogether, funding for NASA’s Mars and Planetary missions in the Fiscal 2013 budget would be sliced by $300 million – from $1.5 Billion this year to $1.2 Billion in 2013. NASA was forced to gut the Mars program to pay for the cost overruns of the James Webb Space Telescope.
Mars rover scientist Prof. Jim Bell of Arizona State University and President of The Planetary Society (TPS) told Universe Today that “no one expects increases”, but cuts of this magnitude are “cause for concern”.
NASA’s robotic missions to Mars and other solar system bodies have been highly successful, resulted in fundamental scientific breakthroughs and are wildly popular with students and the general public.
“With these large proposed cuts to the NASA Mars exploration program, there will be a lot of cause for concern,” said Bell.
“The Mars program has been one of NASA’s crown jewels over the past 15 years, both in terms of science return on investment, and in terms of public excitement and engagement in NASA’s mission. It would also represent an unfortunate retreat from the kind of international collaboration in space exploration that organizations like The Planetary Society so strongly support.”
Bell and other scientists feel that any cuts should be balanced among NASA programs, not aimed only at one specific area.
“Certainly no one expects increasing budgets in these austere times, and it is not useful or appropriate to get into a battle of “my science is better than your science” among the different NASA Divisions and Programs.” Bell told me.
“However, it would be unfortunate if the burden of funding cuts were to befall one of NASA’s most successful and popular programs in a disproportionate way compared to other programs. As Ben Franklin said, “We should all hang together, or surely we will all hang separately.”
Bell added that science minded organizations should work with Congress to influence the debate over the coming months.
“Of course, this would only be an initial proposal for the FY13 and beyond budget. Over the winter, spring, and summer many professional and public organizations, like TPS, will be working with Congress to advocate a balanced program of solar system exploration that focuses on the most important science goals as identified in the recent NRC Planetary Decadal Survey, as well as the most exciting and publicly compelling missions that are supported by the public–who ultimately are the ones paying for these missions.”
“Let’s hope that we can all find a productive and pragmatic way to continue to explore Mars, the outer solar system, and our Universe beyond,” Bell concluded.
“The impact of the cuts … will be to immediately terminate the Mars deal with the Europeans,” said Scott Hubbard, of Stanford University and a former NASA planetary scientist who revived the agency’s Mars exploration program after failures in 1999, to the Washington Post. “It’s a scientific tragedy and a national embarrassment.”
“I encourage whoever made this decision to ask around; everyone on Earth wants to know if there is life on other worlds,” Bill Nye, CEO of The Planetary Society, said in a statement. “When you cut NASA’s budget in this way, you’re losing sight of why we explore space in the first place.”
“There is no other country or agency that can do what NASA does—fly extraordinary flagship missions in deep space and land spacecraft on Mars.” Bill Nye said. “If this budget is allowed to stand, the United States will walk away from decades of greatness in space science and exploration. But it will lose more than that. The U.S. will lose expertise, capability, and talent. The nation will lose the ability to compete in one of the few areas in which it is still the undisputed number one.”
Ed Weiler is NASA’s recently retired science mission chief (now replaced by Grunsfeld) and negotiated the ExoMars program with ESA. Weiler actually quit NASA specifically in opposition to the Mars Program cuts ordered by the Office of Management and Budget (OMB) and had these comments for CBS News;
“To me, it’s bizarro world,” Weiler said an interview with CBS News. “Why would you do this? The President of the United States, President Obama, declared Mars to be the ultimate destination for human exploration. Obviously, before you send humans to the vicinity of Mars or even to land on Mars, you want to know as much about the planet as you possibly can. … You need a sample return mission. The president also established a space policy a few years ago which had the concept of encouraging all agencies to have more and more foreign collaboration, to share the costs and get more for the same bucks.”
“Two years ago, because of budget cuts in the Mars program, I had to appeal to Europe to merge our programs. … That process took two long years of very delicate negotiations. We thought we were following the president’s space policy exactly. Congressional reaction was very positive about our activities. You put those factors in place and you have to ask, why single out Mars? I don’t have an answer.”
Space Analysts and Political leaders also weighed in:
“The president’s budget is just a proposal,” said Howard McCurdy, a space-policy specialist at American University in Washington to the Christian Science Monitor.
The cuts “reflect the new reality” in which the economy, budget deficits, and the federal debt have elbowed their way to the top of Washington’s agenda, McCurdy adds.
“You don’t cut spending for critical scientific research endeavors that have immeasurable benefit to the nation and inspire the human spirit of exploration we all have,” said Rep. John Culberson (R-Tex.). Texas is home to NASA’s Johnson Space Center.
Rep. Adam Schiff (D-CA), who represents the district that’s home to the Jet Propulsion Laboratory (JPL), released this statement following his meeting with NASA Administrator Charles Bolden to discuss the agency’s 2013 budget proposal:
“Today I met with NASA Administrator Charles Bolden to express my dismay over widespread reports that NASA’s latest budget proposes to dramatically reduce the planetary science program, and with it, ground breaking missions to Mars and outer planetary bodies like Jupiter’s icy moon Europa, and to inform him of my vehement opposition to such a move.”
“America’s unique expertise in designing and flying deep-space missions is a priceless national asset and the Mars program, one of our nation’s scientific crown jewels, has been a spectacular success that has pushed the boundaries of human understanding and technological innovation, while also boosting American prestige worldwide and driving our children to pursue science and engineering degrees in college.
“As I told the Administrator during our meeting, I oppose these ill-considered cuts and I will do everything in my power to restore the Mars budget and to ensure American leadership in space exploration.”
In an interview with the San Gabriel Valley Tribune, Schiff said, “What they’re proposing will be absolutely devastating to planetary science and the Mars program. I’m going to be fighting them tooth and nail. Unfortunately if this is the direction the administration is heading, it will definitely hurt JPL – that’s why I’m so committed to reversing this.”
NASA still hopes for some type of scaled back Mars missions in the 2016 to 2020 timeframe which will be outlined in an upcoming article.
In the meantime, the entire future of America’s Search for Life on the Red Planet now hinges on NASA’s Curiosity Mars Science Laboratory rover speeding thru interplanetary space and a pinpoint touchdown inside the layered terrain of Gale Crater on August 6, 2012.
Researchers from the Center of Astrobiology (CAB) in Spain and the Catholic University of the North in Chile have found an “oasis” of microorganisms living two meters beneath the arid soil of the Atacama, proving that even on the driest place on Earth, life finds a way.
Chile’s Atacama Desert receives on average less than .01 cm (.004 inches) of rain per year. In some locations rain has not fallen for over 400 years. But even in this harsh environment there is moisture… just enough, at least, for rock salts and other compounds that can absorb any traces of water to support microbial life beneath the surface.
Using a device called SOLID (Signs Of LIfe Detection) developed by CAB, the researchers were able to identify the presence of microorganisms living on thin films of water within the salty subsurface soil.
Even the substrate itself is able to absorb moisture from the air, concentrating it into films only a few microns thick around the salt crystals. This gives the microorganisms everything they need to survive and flourish — two to three meters underground.
At that depth, there is no sunlight and no oxygen, but there is life.
And even when researchers dug to a depth of five meters (a little over 16 feet) and took samples back to a lab, they were able to not only locate microorganisms but also revive them with the addition of a little water.
Of course, the implications for finding life — or at least the remains of its past existence — on Mars is evident. Mars has been shown to have saline deposits in many regions, and the salt is what helps water remain liquid, longer.
“The high concentration of salt has a double effect: it absorbs water between the crystals and lowers the freezing point, so that they can have thin films of water (in brine) at temperatures several degrees below zero, up to minus 20 C,” said Victor Parro, researcher from the Center of Astrobiology (INTA-CSIC, Spain) and coordinator of the study. This is within the temperature range of many regions of Mars, and also anything located several meters below the surface would be well protected from UV radiation from the Sun.
“If there are similar microbes on Mars or remains in similar conditions to the ones we have found in Atacama, we could detect them with instruments like SOLID,” Parro said.
The development of a new version of the SOLID instrument is currently underway for ESA’s ExoMars program.
Europe scored a major space success with today’s (Feb. 13) flawless maiden launch of the brand new Vega rocket from Europe’s Spaceport in Kourou, French Guiana.
The four stage Vega lifted off on the VV01 flight at 5:00 a.m. EST (10:00 GMT, 11:00 CET, 07:00 local time) from a new launch pad in South America, conducted a perfectly executed qualification flight and deployed 9 science satellites into Earth orbit.
Vega is a small rocket launcher designed to loft science and Earth observation satellites.
The payload consists of two Italian satellites – ASI’s LARES laser relativity satellite and the University of Bologna’s ALMASat-1 – as well as seven picosatellites provided by European universities: e-St@r (Italy), Goliat (Romania), MaSat-1 (Hungary), PW-Sat (Poland), Robusta (France), UniCubeSat GG (Italy) and Xatcobeo (Spain).
Three of these cubesats were the first ever satellites to be built by Poland, Hungary and Romania. They were constructed by University students who were given a once in a lifetime opportunity by ESA to get practical experience and launch their satellites for free since this was Vega’s first flight.
The 30 meter tall Vega has been been under development for 9 years by the European Space Agency (ESA) and its partners, the Italian Space Agency (ASI), French Space Agency (CNES). Seven Member States contributed to the program including Belgium, France, Italy, the Netherlands, Spain, Sweden and Switzerland as well as industry.
ESA can now boast a family of three booster rockets that can service the full range of satellites from small to medium to heavy weight at their rapidly expanding South American Spaceport at the Guiana Space Center.
Vega joins Europe’s stable of launchers including the venerable Ariane V heavy lifter rocket family and the newly inaugurated medium class Russian built Soyuz booster and provides ESA with an enormous commercial leap in the satellite launching arena.
“In a little more than three months, Europe has increased the number of launchers it operates from one to three, widening significantly the range of launch services offered by the European operator Arianespace. There is not anymore one single European satellite which cannot be launched by a European launcher service,” said Jean-Jacques Dordain, Director General of ESA.
“It is a great day for ESA, its Member States, in particularly Italy where Vega was born, for European industry and for Arianespace.”
Dordain noted that an additional 200 workers have been hired in Guiana to meet the needs of Europe’s burgeoning space programs. Whereas budget cutbacks are forcing NASA and its contractors to lay off tens of thousands of people as a result of fallout from the global economic recession.
ESA has already signed commercial contracts for future Vega launches and 5 more Vega rockets are already in production.
Vega’s light launch capacity accommodates a wide range of satellites – from 300 kg to 2500 kg – into a wide variety of orbits, from equatorial to Sun-synchronous.
“Today is a moment of pride for Europe as well as those around 1000 individuals who have been involved in developing the world’s most modern and competitive launcher system for small satellites,” said Antonio Fabrizi, ESA’s Director of Launchers.
America’s hugely successful Mars Exploration program is apparently about to be gutted by Obama Administration officials wielding a hefty budget axe in Washington, D.C. Consequently, Russia has been invited to join the program to replace American science instruments and rockets being scrapped.
NASA’s Fiscal 2013 Budget is due to be announced on Monday, February 13 and its widely reported that the Mars science mission budget will be cut nearly in half as part of a significant decline in funding for NASA’s Planetary Science Division.
The proposed deep slash to the Mars exploration budget would kill NASA’s participation in two new missions dubbed “ExoMars” set to launch in 2016 and 2018 as a joint collaboration with the European Space Agency (ESA).
The ESA/NASA partnership would have dispatched the Trace Gas Orbiter to the Red Planet in 2016 to search for atmospheric methane, a potential signature for microbial life, and an advanced Astrobiology rover to drill deeper into the surface in 2018. These ambitious missions had the best chance yet to determine if Life ever evolved on Mars.
The 2016 and 2018 ExoMars probes were designed to look for evidence of life on Mars and set the stage for follow on missions to retrieve the first ever soil samples from the Red Planet’s surface and eventually land humans on Mars.
The proposed Mars budget cuts will obliterate these top priority science goals for NASA.
The BBC reports that “ a public announcement by NASA of its withdrawal from the ExoMars program will probably come once President Obama’s 2013 Federal Budget Request is submitted.”
A Feb. 9 article in ScienceInsider, a publication of the journal Science, states that “President Barack Obama will propose a $300 million cut in NASA’s planetary science programs as part of his 2013 request for the agency.”
This would amount to a 20% cut from $1.5 Billion in 2012 to $1.2 Billion in 2013. The bulk of that reduction is aimed squarely at purposefully eliminating the ExoMars program. And further deep cuts are planned in coming years !
The Mars budget of about $580 million this year would be radically reduced by over $200 million, thereby necessitating the end of NASA’s participation in ExoMars. These cuts will have a devastating impact on American scientists and engineers working on Mars missions.
The fallout from the looming science funding cuts also caused one longtime and top NASA manager to resign.
According to ScienceInsider, Ed Weiler, NASA’s science mission chief, says he “quit NASA Over Cuts to Mars Program.”
“The Mars program is one of the crown jewels of NASA,” said Ed Weiler to ScienceInsider.
“In what irrational, Homer Simpson world would we single it out for disproportionate cuts?”
“This is not about the science mission directorate, this is not even about NASA. This is about the country. We are the only country in the world that has demonstrated the capability to land anything on Mars. How can we allow that to be undermined?”
Weiler’s resignation from NASA on Sept. 30, 2011 was sudden and quick, virtually from one day to the next. And it came shortly after the successful launch of NASA’s GRAIL lunar probes, when I spoke to Weiler about Mars and NASA’s Planetary Science missions and the gloomy future outlook. Read my earlier Universe Today story about Weiler’s retirement.
Ed Weiler was the Associate Administrator for NASA’s Science Mission Directorate (SMD) and his distinguished career spanned almost 33 years.
The dire wrangling over NASA’s 2013 budget has been ongoing for many months and some of the funding reductions had already leaked out. For example NASA had already notified ESA that the US could not provide funding for the Atlas V launchers in 2016 and 2018. Furthermore, Weiler and other NASA managers told me the 2018 mission was de-scoped from two surface rovers down to just one to try and save the Mars mission program.
ESA is now inviting Russian participation to replace the total American pullout, which will devastate the future of Red Planet science in the US. American scientists and science instruments would be deleted from the 2016 and 2018 ExoMars missions.
The only approved US mission to Mars is the MAVEN orbiter due to blastoff in 2013 – and there are NO cameras aboard MAVEN.
NASA is caught in an inescapable squeeze between rising costs for ongoing and ambitious new missions and an extremely tough Federal budget environment with politicians of both political affiliations looking to cut what they can to rein in the deficit, no matter the consequences of “killing the goose that laid the golden egg”.
NASA Watch Editor Keith Cowing wrote; “Details of the FY 2013 NASA budget are starting to trickle out. One of the most prominent changes will be the substantial cut to planetary science at SMD [NASA’s Science Mission Directorate]. At the same time, the agency has to eat $1 billion in Webb telescope overruns – half of which will come out of SMD.”
The cost of the James Webb Space Telescope (JWST) has skyrocketed to $8.7 Billion.
To pay for JWST, NASA is being forced to gut the Mars program and other science missions funded by the same Science Mission Directorate that in the past and present has stirred the public with a mindboggling payoff of astounding science results from many missions that completely reshaped our concept of humankinds place in the Universe.
Meanwhile, China’s space program is rapidly expanding and employing more and more people. China’s scientific and technological prowess and patent applications are increasing and contributing to their fast growing economy as American breakthroughs and capabilities are diminishing.
Under the budget cutting scenario of no vision, the Curiosity Mars Science Laboratory rover will be America’s last Mars rover for a long, long time. Curiosity will thus be the third and last generation of US Mars rovers – 4th generation to be Axed !
New measurements from ESA’s Venus Express spacecraft shows that Venus’ rotation rate is about 6.5 minutes slower than previous measurements taken 16 years ago by the Magellan spacecraft. Using infrared instruments to peer through the planet’s dense atmosphere, Venus Express found surface features weren’t where the scientists expected them to be.
“When the two maps did not align, I first thought there was a mistake in my calculations as Magellan measured the value very accurately, but we have checked every possible error we could think of,” said Nils Müller, a planetary scientist at the DLR German Aerospace Centre, lead author of a research paper investigating the rotation.
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Using the VIRTIS infrared instrument, scientists discovered that some surface features were displaced by up to 20 km from where they should be given the accepted rotation rate as measured by the Magellan orbiter in the early 1990s.
Over its four-year mission, Magellan determined the length of the day on Venus as being equal to 243.0185 Earth days. But the data from Venus Express indicate the length of the Venus day is on average 6.5 minutes longer.
What could cause the planet to slow down? One possibility may be the raging weather on Venus. Recent atmospheric models have shown that the planet could have weather cycles stretching over decades, which could lead to equally long-term changes in the rotation period. The most important of those forces is due to the dense atmosphere – more than 90 times the pressure of Earth’s and high-speed weather systems, which are believed to change the planet’s rotation rate through friction with the surface.
Earth experiences a similar effect, where it is largely caused by wind and tides. The length of an Earth day can change by roughly a millisecond and depends seasonally with wind patterns and temperatures over the course of a year.
But a change of 6.5 minutes over a little more than a decade is a huge variation.
Other effects could also be at work, including exchanges of angular momentum between Venus and the Earth when the two planets are relatively close to each other. But the scientists are still working to figure out the reason for the slow down.
These detailed measurements from orbit are also helping scientists determine whether Venus has a solid or liquid core, which will help our understanding how the planet formed and evolved. If Venus has a solid core, its mass must be more concentrated towards the center. In this case, the planet’s rotation would react less to external forces.
“An accurate value for Venus’ rotation rate will help in planning future missions, because precise information will be needed to select potential landing sites,” said Håkan Svedhem, ESA’s Venus Express project scientist.
Venus Express will keep monitoring the planet to determine if the rate of rotation continues to change.