NASA’s Curiosity rover is using a new experiment to better understand the history of the Martian atmosphere by analyzing xenon.
While NASA’s Curiosity rover concluded its detailed examination of the rock layers of the “Pahrump Hills” in Gale Crater on Mars this winter, some members of the rover team were busy analyzing the Martian atmosphere for xenon, a heavy noble gas.
Curiosity’s Sample Analysis at Mars (SAM) experiment analyzed xenon in the planet’s atmosphere. Since noble gases are chemically inert and do not react with other substances in the air or on the ground, they are excellent tracers of the history of the atmosphere. Xenon is present in the Martian atmosphere at a challengingly low quantity and can be directly measured only with on-site experiments such as SAM.
“Xenon is a fundamental measurement to make on a planet such as Mars or Venus, since it provides essential information to understand the early history of these planets and why they turned out so differently from Earth,” said Melissa Trainer, one of the scientists analyzing the SAM data.
A planetary atmosphere is made up of different gases, which are in turn made up of variants of the same chemical element called isotopes. When a planet loses its atmosphere, that process can affect the ratios of remaining isotopes.
Measuring xenon tells us more about the history of the loss of the Martian atmosphere. The special characteristics of xenon – it exists naturally in nine different isotopes, ranging in atomic mass from 124 (with 70 neutrons per atom) to 136 (with 82 neutrons per atom) – allows us to learn more about the process by which the layers of atmosphere were stripped off Mars than using measurements of other gases.
A process removing gas from the top of the atmosphere removes lighter isotopes more readily than heavier ones, leaving a ratio higher in heavier isotopes than it was originally.
The SAM measurement of the ratios of the nine xenon isotopes traces a very early period in the history of Mars when a vigorous atmospheric escape process was pulling away even the heavy xenon gas. The lighter isotopes were escaping just a bit faster than the heavy isotopes.
Those escapes affected the ratio of isotopes in the atmosphere left behind, and the ratios today are a signature retained in the atmosphere for billions of years. This signature was first inferred several decades ago from isotope measurements on small amounts of Martian atmospheric gas trapped in rocks from Mars that made their way to Earth as meteorites.
“We are seeing a remarkably close match of the in-situ data to that from bits of atmosphere captured in some of the Martian meteorites,” said SAM Deputy Principal Investigator Pan Conrad.
SAM previously measured the ratio of two isotopes of a different noble gas, argon. The results pointed to continuous loss over time of much of the original atmosphere of Mars.
The xenon experiment required months of careful testing at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, using a close copy of the SAM instrument enclosed in a chamber that simulates the Mars environment. This testing was led by Goddard’s Charles Malespin, who developed and optimized the sequence of instructions for SAM to carry out on Mars.
“I’m gratified that we were able to successfully execute this run on Mars and demonstrate this new capability for Curiosity,” said Malespin.
NASA’s Mars Science Laboratory Project is using Curiosity to determine if life was possible on Mars and study major changes in Martian environmental conditions. NASA studies Mars to learn more about our own planet, and in preparation for future human missions to Mars. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the project for NASA’s Science Mission Directorate in Washington.
New simulations of the most energetic collisions in the universe are helping astrophysicists understand how gravitational waves are generated, possibly giving us an exciting glimpse into the future of gravitational astronomy.
Black hole mergers are thought to be the most energetic events the universe has seen since the Big Bang, nearly 14 billion years ago. These events occur when two (or more) spinning black holes become trapped in their mutual gravitational wells, orbit and then collide, merging as one. The energy generated in these merging events are thought to create a very specific signature of gravitational wave emissions.
According to Einstein’s theory of general relativity, gravitational waves should be created when massive objects accelerate through space. However, they have not been directly observed. Indirectly, we can see their impact when white dwarf binaries, for example, orbit one another — over time, as their orbits shrink, energy is lost. This energy must be carried away from the system by gravitational waves.
Although we have a pretty good idea about their properties, gravitational waves are notoriously difficult to detect directly, but should they become detectable in the future, a new era of gravitational astronomy may be possible. And black hole mergers could be the key to making this happen.
“An accelerating charge, like an electron, produces electromagnetic radiation, including visible light waves,” Michael Kesden, of the University of Texas at Dallas, said in a press release. “Similarly, any time you have an accelerating mass, you can produce gravitational waves.”
Kesden is the lead author of new research into black hole mergers published in the journal Physical Review Letters.
“Using gravitational waves as an observational tool, you could learn about the characteristics of the black holes that were emitting those waves billions of years ago, information such as their masses and mass ratios, and the way they formed,” added co-author Davide Gerosa, of the University of Cambridge, UK. “That’s important data for more fully understanding the evolution and nature of the universe.”
Currently, there are several projects underway that are attempting to detect gravitational waves. Perhaps the most famous detector is the Laser Interferometer Gravitational-Wave Observatory (LIGO) situated at two locations in the US — in Louisiana and Washington. LIGO is set up to detect the passage of gravitational waves through our local volume of space.
Using precision lasers along two 4 kilometer-long tunnels in “L” shaped structures, the very slight perturbations of spacetime should be detectable as gravitational waves pass through our planet. Although LIGO has yet to detect a positive gravitational wave signal, it is currently undergoing upgrades that will boost its sensitivity. “Advanced LIGO” is scheduled to go online later this year. Europe is also building its own detector called VIRGO and the LISA Pathfinder Mission is planned to set up a gravitational wave detector in space.
“The equations that we solved will help predict the characteristics of the gravitational waves that LIGO would expect to see from binary black hole mergers,” said co-author Ulrich Sperhake, also of the University of Cambridge. “We’re looking forward to comparing our solutions to the data that LIGO collects.”
The researchers have specifically focused on modelling the spin and precession of binary black holes as they orbit one another.
“Like a spinning top, black hole binaries change their direction of rotation over time, a phenomenon known as procession,” said Sperhake. “The behavior of these black hole spins is a key part of understanding their evolution.”
“With these solutions, we can create computer simulations that follow black hole evolution over billions of years,” said Kesden. “A simulation that previously would have taken years can now be done in seconds. But it’s not just faster. There are things that we can learn from these simulations that we just couldn’t learn any other way.”
The researchers hope that, with the help of their computer models, new details behind black hole mergers may be revealed. In doing so, the specific gravitational wave signal may be characterized so that when detectors such as Advanced LIGO register their first signals, we may quickly untangle what is generating the emission.
Like optical astronomy revolutionized our naked eye view on the universe and X-ray astronomy highlighted some of the most energetic phenomena in the cosmos, gravitational wave astronomy could give us a view of a previously invisible realm — a realm of massive interactions and collisions that characterize the very evolution of our universe.
Planets with four suns in their sky may be more common than previously thought, a new study suggests.
Astronomers have spotted a fourth star in a planetary system called 30 Ari, bringing the number of known planet-harboring quadruple-sun systems to two. Numerous two- and three-star exoplanets have been identified.
“Star systems come in myriad forms. There can be single stars, binary stars, triple stars, even quintuple star systems,” study lead author Lewis Roberts, of NASA’s Jet Propulsion Laboratory in Pasadena, California, said in a statement. “It’s amazing the way nature puts these things together.”
30 Ari lies 136 light-years from the sun in the constellation Aries. Astronomers discovered a giant planet in the system in 2009; the world is about 10 times more massive than Jupiter and orbits its primary star every 335 days. A second pair of stars lies approximately 1,670 astronomical units (AU) away. (1 AU is the distance between Earth and the sun — about 93 million miles, or 150 million kilometers).
Roberts and his colleagues used the new “Robo-AO” adaptive optics system at the Palomar Observatoryin California to sweep the sky, examining hundreds of stars each evening for signs of multiplicity. This search identified a fourth star in close proximity to 30 Ari’s primary star.
A diagram of the newfound system show the two pairs of stars in orbit together, while a planet circles one of them.
The newfound star circles its companion once every 80 years, at a distance of just 22 AU, but it does not appear to affect the exoplanet’s orbit despite such proximity. This is a surprising result that will require further observations to understand, researchers said.
To a hypothetical observer cruising through the giant planet’s atmosphere, the sky would appear to host one small sun and two bright stars visible in daylight. With a large enough telescope, one of the bright stars could be resolved into a binary pair.
The discovery marks just the second time a planet has been identified in a four-star system. The first four-star planet, PH1b or Kepler-64b, was spotted in 2012 by citizen scientistsusing publicly available data from NASA’s Kepler mission.
Planets with multiple suns have become less of a novelty in recent years, as astronomers have found a number of real worlds that resemble Tatooine, Luke Skywalker’s home planet in the Star Warsfilms.
Indeed, binary stars are more commonthan their singleton counterparts. And the new study suggests that more planetary systems with two pairs of binary stars may be discovered down the road.
“About four percent of solar-type stars are in quadruple systems, which is up from previous estimates because observational techniques are steadily improving,” co-author Andrei Tokovinin, of the Cerro Tololo Inter-American Observatory in Chile, said in the same statement.
In addition to finding a fourth star around 30 Ari, the team also found a third star in a planetary system previously thought to have only two suns.
This system, known as HD 2638, was already known to host a planet with half the mass of Jupiter rushing around its primary star once every 3.4 days, while a second star lies about 44,000 AU, or 0.7 light-years, away. The newly discovered third star sits just 28 AU from the primary star, and it appears to have influenced the orbit of the gaseous planet, researchers said.
NASA’s Low-Density Supersonic Decelerator (LDSD) project will be flying a rocket-powered, saucer-shaped test vehicle into near-space from the Navy’s Pacific Missile Range Facility on Kauai, Hawaii, in June.
The public is invited to tune in to an hour-long live, interactive video broadcast from the gallery above a clean room at NASA’s Jet Propulsion Laboratory in Pasadena, California, where this near-space experimental test vehicle is being prepared for shipment to Hawaii. During the broadcast, the 15-foot-wide, 7,000-pound vehicle is expected to be undergoing a “spin-table” test. The event will be streamed live on www.ustream.tv/NASAJPL2 on March 31, from 9 a.m. to 10 a.m. PDT. JPL’s Gay Hill will host the program while LDSD team members will answer questions submitted to the Ustream chat box or via Twitter using the #AskNASA hashtag.
The LDSD crosscutting demonstration mission will test breakthrough technologies that will enable large payloads to be safely landed on the surface of Mars, or other planetary bodies with atmospheres, including Earth. The technologies will not only enable landing of larger payloads on Mars, but also allow access to much more of the planet’s surface by enabling landings at higher-altitude sites.
More information about the LDSD space technology demonstration mission is online at:
The LDSD mission is part of NASA’s Space Technology Mission Directorate, which is innovating, developing, testing and flying hardware for use in future missions. NASA’s technology investments provide cutting-edge solutions for our nation’s future. For more information about the directorate, visit:
A team using the Sample Analysis at Mars (SAM) instrument suite aboard NASA’s Curiosity rover has made the first detection of nitrogen on the surface of Mars from release during heating of Martian sediments.
The nitrogen was detected in the form of nitric oxide, and could be released from the breakdown of nitrates during heating. Nitrates are a class of molecules that contain nitrogen in a form that can be used by living organisms. The discovery adds to the evidence that ancient Mars was habitable for life.
Nitrogen is essential for all known forms of life, since it is used in the building blocks of larger molecules like DNA and RNA, which encode the genetic instructions for life, and proteins, which are used to build structures like hair and nails, and to speed up or regulate chemical reactions.
However, on Earth and Mars, atmospheric nitrogen is locked up as nitrogen gas (N2) – two atoms of nitrogen bound together so strongly that they do not react easily with other molecules. The nitrogen atoms have to be separated or “fixed” so they can participate in the chemical reactions needed for life. On Earth, certain organisms are capable of fixing atmospheric nitrogen and this process is critical for metabolic activity. However, smaller amounts of nitrogen are also fixed by energetic events like lightning strikes.
Nitrate (NO3) – a nitrogen atom bound to three oxygen atoms – is a source of fixed nitrogen. A nitrate molecule can join with various other atoms and molecules; this class of molecules is known as nitrates.
There is no evidence to suggest that the fixed nitrogen molecules found by the team were created by life. The surface of Mars is inhospitable for known forms of life. Instead, the team thinks the nitrates are ancient, and likely came from non-biological processes like meteorite impacts and lightning in Mars’ distant past.
Features resembling dry riverbeds and the discovery of minerals that form only in the presence of liquid water suggest that Mars was more hospitable in the remote past. The Curiosity team has found evidence that other ingredients needed for life, such as liquid water and organic matter, were present on Mars at the Curiosity site in Gale Crater billions of years ago.
“Finding a biochemically accessible form of nitrogen is more support for the ancient Martian environment at Gale Crater being habitable,” said Jennifer Stern of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Stern is lead author of a paper on this research published online in the Proceedings of the National Academy of Science March 23.
The team found evidence for nitrates in scooped samples of windblown sand and dust at the “Rocknest” site, and in samples drilled from mudstone at the “John Klein” and “Cumberland” drill sites in Yellowknife Bay. Since the Rocknest sample is a combination of dust blown in from distant regions on Mars and more locally sourced materials, the nitrates are likely to be widespread across Mars, according to Stern. The results support the equivalent of up to 1,100 parts per million nitrates in the Martian soil from the drill sites. The team thinks the mudstone at Yellowknife Bay formed from sediment deposited at the bottom of a lake. Previously the rover team described the evidence for an ancient, habitable environment there: fresh water, key chemical elements required by life, such as carbon, and potential energy sources to drive metabolism in simple organisms.
The samples were first heated to release molecules bound to the Martian soil, then portions of the gases released were diverted to the SAM instruments for analysis. Various nitrogen-bearing compounds were identified with two instruments: a mass spectrometer, which uses electric fields to identify molecules by their signature masses, and a gas chromatograph, which separates molecules based on the time they take to travel through a small glass capillary tube — certain molecules interact with the sides of the tube more readily and thus travel more slowly.
Along with other nitrogen compounds, the instruments detected nitric oxide (NO — one atom of nitrogen bound to an oxygen atom) in samples from all three sites. Since nitrate is a nitrogen atom bound to three oxygen atoms, the team thinks most of the NO likely came from nitrate which decomposed as the samples were heated for analysis. Certain compounds in the SAM instrument can also release nitrogen as samples are heated; however, the amount of NO found is more than twice what could be produced by SAM in the most extreme and unrealistic scenario, according to Stern. This leads the team to think that nitrates really are present on Mars, and the abundance estimates reported have been adjusted to reflect this potential additional source.
“Scientists have long thought that nitrates would be produced on Mars from the energy released in meteorite impacts, and the amounts we found agree well with estimates from this process,” said Stern.
The SAM instrument suite was built at NASA Goddard with significant elements provided by industry, university, and national and international NASA partners. NASA’s Mars Science Laboratory Project is using Curiosity to assess ancient habitable environments and major changes in Martian environmental conditions. NASA’s Jet Propulsion Laboratory in Pasadena, California, a division of the California Institute of Technology, built the rover and manages the project for NASA’s Science Mission Directorate in Washington. The NASA Mars Exploration Program and Goddard Space Flight Center provided support for the development and operation of SAM. SAM-Gas Chromatograph was supported by funds from the French Space Agency (CNES). Data from these SAM experiments are archived in the Planetary Data System (pds.nasa.gov).
Source: Jet Propulsion Laboratory
Many planets in our solar system have more than one moon. Mars has two moons, Jupiter has 67, Saturn 62, Uranus 27, Neptune 14. Those numbers keep changing, and you can see a relatively current count of solar system moons here from NASA’s Jet Propulsion Laboratory. It makes sense that the outer worlds, with their stronger gravity, would have more moons. Meanwhile, our planet Earth has just one moon. Doesn’t it?
Moons are defined as Earth’s natural satellites. They orbit around the Earth. And, in fact, although Earth sometimes has more than one moon, some objects you might have heard called Earth’s second moon aren’t, really. Let’s talk about some non-moons first.
3753 Cruithne in 2001. Astronomer Duncan Waldron discovered this faint asteroid on October 10, 1986, on a photographic plate taken with the UK Schmidt Telescope at Siding Spring Observatory in Australia. Image via Sonia Keys via Wikimedia Commons.
The orbits around the sun of Cruithne and Earth over the course of a year (from September 2007 to August 2008).
Quasi-satellites are not second moons for Earth.
A quasi-satellite is an object in a co-orbital configuration with Earth (or another planet). Scientists would say there is a 1:1 orbital resonance between Earth and this object. In other words, a quasi-satellite is orbiting the sun, just as Earth is. Its orbit around the sun takes exactly the same time as Earth’s orbit, but the shape of the orbit is slightly different.
The most famous quasi-satellite in our time – and an object you might have heard called a second moon for Earth – is 3753 Cruithne. This object is five kilometers – about three miles – wide. Notice it has an asteroid name. That’s because it is an asteroid orbiting our sun, one of several thousand asteroids whose orbits cross Earth’s orbit. Astronomers discovered Cruithne in 1986, but it wasn’t until 1997 that they figured out its complex orbit. It’s not a second moon for Earth; it doesn’t orbit Earth. But Cruithne is co-orbiting the sun with Earth. Like all quasi-satellites, Cruithne orbits the sun once for every orbit of Earth.
As seen from Earth Cruithne has what is known as a horseshoe orbit. In other words, viewed from Earth, it appears to orbit a point beside Earth.
Earth’s gravity affects Cruithne, in such a way that Earth and this asteroid return every year to nearly the same place in orbit relative to each other. However, Cruithne won’t collide with Earth, because its orbit is very inclined with respect to ours. It moves in and out of the plane of the ecliptic, or plane of Earth’s orbit around the sun.
Orbits like that of Cruithne aren’t stable. Computer models indicate that Cruithne will spend only another 5,000 years or so in its current orbit. That’s a blink on the long timescale of our solar system. The asteroid might then move into true orbit around Earth for a time, at which time it would be a second moon – but not for long. Astronomers estimate that, after 3,000 years orbiting Earth, Cruithne would escape back into orbit around the sun.
By the way, Cruithne isn’t the only quasi-satellite in a 1:1 resonance orbit with Earth. The objects 2010 SO16 and (277810) 2006 FV35, among others, are also considered quasi-satellites to Earth.
These objects are not second moons for Earth, although sometimes you might hear people mistakenly say they are. Does Earth ever have more than one moon? Surprisingly (or not), the answer is yes.
Asteroids that are captured temporarily by Earth’s gravity have crazy orbits around us, because they’re pulled from all sides by the Earth, sun and moon. Image Credit: K. Teramuru, UH Ifa
Earth does sometimes have temporary moons. In March of 2012, astronomers at Cornell University published the result of a computer study, suggesting that asteroids orbiting the sun might temporarily become natural satellites of Earth. In fact, they said, Earth usually has more than one temporary moon, which they called minimoons. These astronomers said the minimoons would follow complicated paths around Earth for a time, as depicted in the images above and below. Eventually, they would break free of Earth’s gravity – only to be immediately recaptured into orbit around the sun, becoming an asteroid once more. The little moons envisioned by these astronomers might typically be only a few feet across and might orbit our planet for less than a year before going back to orbit the sun as asteroids.
Diagram of the orbit for 2006 RH120 during a period of time that it is orbiting the Earth during a temporary satellite capture event. Image via Wikimedia Commons.
Have astronomers detected any of these minimoons? Yes. Writing in the magazine Astronomy in December 2010, Donald Yeomans (Manager of NASA’s Near-Earth Object Program Office at NASA’s Jet Propulsion Laboratory) described an object discovered in 2006 that appears to fit that description. The object – now designated 2006 RH120 – is estimated to be 5 meters (about 15 feet) in diameter. Yeomans said that, when this object was discovered in a near-polar orbit around Earth, it was thought at first to be a third stage Saturn S-IVB booster from Apollo 12, but later determined to be an asteroid. 2006 RH120 began orbiting the sun again 13 months after its discovery, but it’s expected to sweep near Earth and be re-captured as a minimoon by Earth’s gravity later in this century.
Bottom line: That asteroid called 3753 Cruithne is not a second moon for Earth, but its orbit around the sun is so strange that you still sometimes hear people say it is. Meanwhile, astronomers have suggested that Earth does frequently capture asteroids, which might orbit our world for about a year before breaking free of Earth’s gravity and orbiting the sun once more.