In October 2015 Curiosity used the camera at the end of its mechanical arm to take a self portrait inside Gale Crater
Tuesday, March 28, 2017
MDRS Crew 176-Final Mission Report
|
|
Monday, March 27, 2017
Solving The Mysteries of The Din-Killing Crater
Solving the mysteries of the dino-killing craterThe impact crater from the event that kicked off the extinction of the dinosaurs is providing clues that might one day help understand the history of life on Mars.
Artist impression of the Chicxulub crater, showing the peak ring.
Scientists drilling into the floor of the Chicxulub impact crater in the Gulf of Mexico are working to increase our understanding of cratering processes on the Moon and other worlds, and to find geological signatures that might aid the search for ancient habitable zones on Mars.
The Chicxulub crater was formed 66 million years ago when a 10-kilometre-wide asteroid or comet smashed into the sea near Mexico’s Yucatan Peninsula.
The impact launched a global catastrophe widely believed to have killed off the dinosaurs. But it is also an excellent earthly opportunity to observe geological processes similar to those that occurred in large impact craters on Mars or the Moon, says Gail Christeson, a geophysicist from the University of Texas-Austin.
Christeson was part of an international ocean-science project called IODP-ICDP Expedition 364, which in the spring of 2016 drilled through seabed sediments to extract an 832-metre core from the crater’s peak ring.
Peak rings are circular mountain ranges formed within the rims of large impact craters. They are created, Chriteson says, when crustal rocks rebound after being pressed deep into the earth by the impact.
In smaller craters the result is a central peak. But in large ones, she says, the peak rises so high that its center collapses inward under its own weight, leaving a ring around what would have been its base.
Such craters are easily visible on the Moon, Mercury, and Mars, but are not as obvious on Earth, where geological processes have hidden them from view.
In the case of Chicxulub, the peak ring is about 80-90 kilometers across (compared to 180 kilometres for the crater itself). One of the purposes of drilling into it, says Christeson, was to study the rock and determine its seismic properties in order to help researchers confirm their seismic maps of the crater as a whole.
But in the process, she says, they also confirmed the theory that the rocks now comprising the peak ring had risen to their present locations from depths of about 10 kilometres via the force of the rebound.
Another finding was that the rocks of the peak ring were very porous. Even though many of them were granite, Christeson says, they, had porosities of eight to 10%.
“That’s really, really high,” she says. “Granite is normally less than 1%.”
Other rocks – a type of conglomerate known as a breccia – had porosities of 30 to 40%.
These impact-shattered items, says Aurial Rae, a geologist from Imperial College London, provided pathways for water to circulate through deep, impact-heated rocks, creating hydrothermal systems much like those found today along mid-ocean ridges.
Proof of this, he says, comes from the existence of hydrothermally altered material throughout the length of the drill core. And while the core represents only a single location in the peak ring, there is no reason to believe it isn’t typical.
“I would expect that there was an active hydrothermal system going throughout the entire peak ring,” Rae says.
In fact, he notes, it probably extended well below the bottom of the core, to a depth of about 3000 metres.
This circulation appears to have gone on for a long time, adds Sonia Tikoo, a planetary scientist from Rutgers University in New Jersey. Tikoo’s specialty is paleomagnetism, the study of the magnetic properties of ancient rocks.
When rocks are formed, she says, they record the direction and strength of the Earth’s magnetic field. But the circulation of chemical-laden hot water in hypothermal systems can alter this, resetting magnetic orientations to that of when the change occurred.
This is useful for geologists, because every few hundred thousand years the Earth’s magnetic field reverses direction. At the time of the Chicxulub impact it was pointing in the opposite direction from today. But 300,000 years later it flipped.
Hydrothermally altered rocks within the core show signs of both orientations, Tikoo says, indicating that the hydrothermal system must have lasted at least long enough to experience the transition.
In fact, she adds, modeling work done by David Kring, a geologist at the Lunar and Planetary Institute in Houston, Texas, has shown that it’s possible that hydrothermal circulation in the peak ring might have continued for one-to-two million years after the impact.
“But there wasn’t any experimental data,” she says. “This provided the first experimental evidence that it lasted at least 300,000 years.”
Understanding these processes, the scientists say, can be helpful in determining if life existed on other worlds, especially Mars. “What we’re looking for is what we can learn that relates to hypothermal systems on other planets where we might expect to find life, says Rae.
Chris McKay a planetary scientist and astrobiologist at NASA Ames Research Center, Moffett Field, California, agrees. Much of Mars is heavily cratered, he says, adding that impact-induced hydrothermal systems in these craters could have been an important habitat for life.
In fact, he notes, “Gale Crater—the site of Curiosity's roving—is an impact crater, and the sort of hydrothermal circulation they are seeing in Chicxulub would also be expected there. Could be Curiosity will find some evidence for this as it traverses further.”
|
|
The Asteroid Mission That Trump Cancelled
NASA, ESA aim to ram asteroid
A joint mission by NASA and ESA is set to smack into an asteroid in a rehearsal for saving the Earth.
Artist's impression of the binary asteroid Didymos, the ESA satellite watching, the NASA satellite heading in for impact.
ESA/GETTY IMAGES
A planned NASA and European Space Agency (ESA) joint mission is poised to test whether it is possible to knock an asteroid from one orbit into another.
The mission, which has not yet fully funded, is part of the space agencies’ focus on “planetary defence”: the protection of Earth from collision with dangerous asteroids.
But instead of trying to blow up such a threat, as in the 1998 science fiction movie Armageddon, the Asteroid Impact and Deflection Assessment mission intends to prove that an asteroid can be shifted by hitting it with a fast-moving spacecraft launched from Earth.
“We save Bruce Willis’s life,” quips Patrick Michel, a planetary scientist from the Observatoire de la Côte d’Azur, in Nice, France, in a reference to the movie. “He doesn’t have to sacrifice himself.”
The mission uses two spacecraft, one to be launched by ESA in 2020, the other by NASA in 2021.
The ESA spacecraft, called AIM (for Asteroid Impact Mission) will rendezvous with the selected asteroid and go into orbit around it in early 2022.
The NASA spacecraft, called DART (Double Asteroid Redirection Test) will be timed to hit the rock a few months later, at a speed of six kilometres per second, while the AIM spacecraft and earthbound telescopes watch.
The target is a moonlet of 65803 Didymos, a near-Earth asteroid discovered in 1996. At the time of impact it will be about 11 million kilometres away.
As the world “double” in the DART mission’s name suggests, Didymos is a binary system, meaning that there are two asteroids orbiting each other. The large one is about 800 metres across; the moonlet measures about 160 metres.
The impact is expected to alter the moonlet’s orbital speed around Didymos by about a half-millimetre per second, says Andrew Cheng, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, who is lead investigator for the NASA side of the project.
“That doesn’t sound like much, but it is very easily measured, both by the AIM spacecraft and by telescopes on the ground,” he said, speaking by phone from the 2017 Lunar and Planetary Science Conference in the Woodlands, Texas, where he is presenting details on the project.
The effect is easy to measure from Earth, he adds, because the moonlet’s orbit is aligned so that viewed from down here it passes behind Didymos once each circuit.
These disappearances make it easy to precisely measure its orbital period, Cheng says, estimating that even the tiny speed change expected to be imparted by the crash will alter its 11.9-hour orbit by several minutes.
One of the goals of the mission is to test whether it is possible to hit such a small, distant object with a spacecraft moving at such a high speed. But it’s also important, Cheng says, to see how the asteroid responds to the impact.
That’s because hitting an asteroid with a spacecraft isn’t like hitting a billiard ball with the cue ball.
"When we have a high-speed impact on an asteroid, you create a crater,” Cheng says. “You blow pieces back in the direction you came from.”
The ejection of this material shoves the asteroid in the opposite direction, significantly increasing its momentum change.
“The amount can be quite large,” Cheng says, “More than a factor of two.”
With the AIM spacecraft orbiting nearby, the impact will also allow the first scientific measurements of precisely what happens when an asteroid (or moon) gets hit by a fast-moving object, such as the 500-kilogram DART spacecraft.
“This will tell us about cratering processes,” says Michel, who is the lead investigator of the ESA side of the mission.
That is important because planetary scientists use crater counts on other worlds to help determine how old their surfaces are, based on the numbers and sizes of objects that have hit the surface since it formed.
But most of the research designed to correlate crater size to the size of the impactor rests either on modeling or small-scale laboratory tests.
This is the first time, Cheng says, that scientists will be able to test their models by looking at a crater on an asteroid, knowing exactly what hit it and how fast it was moving. Michel adds that the target moonlet will also be the smallest asteroid ever to be visited by a spacecraft.
“This is important for science and for companies interested in asteroid mining because so far we don’t have any data regarding what we will find on the surface of such a small body,” he says.
“Each time we discover a new world we have surprises,” he adds. “The main driver [of this mission] is planetary defence, but it has a lot of scientific implicaitons.”
Saturday, March 25, 2017
The Curiosity Mars Rover Wheels Are Starting To Break
The Curiosity Mars rover's wheels are starting to break
Not even space robots are immune to the effects of old age
Since August of 2012, NASA's Curiosity Rover has tooled around the red planet doing science for us Earthlings. Now, nearly five years and some 10 miles later, the robot is starting to experience the wear and tear of an aging machine: On Tuesday, NASA announced the first two breaks in the rover's wheel treads.
This isn't surprising—or even particularly upsetting—news, no matter how much you love NASA's youngest Martian robot. It may seem strange for there to be wear and tear with just 10 miles, but it took quite a few years to rack up those miles and all of that super-slow rolling over rocky terrain is just bound to cause some damage. Curiosity has already lived twice as long as planned in its primary mission. And NASA scientists have been keeping an eye on the rover's aging wheels for awhile now. These might be the first breaks in the grousers that give Curiosity traction, but they certainly aren't the first markups on otherwise pristine wheels: The reason NASA is keeping such a close eye on the wheels is that sharp rocks and grit have already left them pock-marked.
Curiosity may have outlived its initial mission, but it's got nothing on its big sister Opportunity, which has already exceeded its expected shelf-life by almost 13 years (and completed the equivalent of one very slow marathon). So one wonders: what's the prognosis for Curiosity?
According to on-Earth wheel longevity testing, NASA believes that "when three grousers on a wheel have broken, that wheel has reached about 60 percent of its useful life". The two grousers that broke sometime between January and March are both on the left middle wheel, so that guy is a hope and a prayer away from being more than halfway through its lifespan.
That...is not bad. Yes, one of the robot's wheels is now close to reaching a milestone we wish it never had to reach. But even if it hit that old-age benchmark tomorrow, the outlook would still be good: Curiosity is currently climbing up Mount Sharp to study Martian climate records trapped inside layers of rock, and has its sights set on areas thought to contain chemically interesting things like sulfates and clays—areas that might show evidence of past or present liquid water. But getting to those new targets will put less than five miles on its odometer.
"This is an expected part of the life cycle of the wheels and at this point does not change our current science plans or diminish our chances of studying key transitions in mineralogy higher on Mount Sharp," Curiosity Project Scientist Ashwin Vasavada said in a statement.
Still, it's miserable being reminded that two favorite space robots can't live forever. Gather ye rosebuds while ye may, Curiosity, and fire that space laser of yours at will.
 |
Click here to Reply or Forward
|
Wednesday, March 22, 2017
Mars May Have Had A Ring In The Past And Might Have One In The Future
Mars May Have Had a Ring in the Past and Could Have One in the Future
The red planet’s moon may have broken apart into a ring of debris and reformed several times over the planet’s history
Saturn’s rings are, of course, a defining feature of the planet. But the other gas giants in the Solar System—Jupiter, Neptune and Uranus—also have faint, dark systems of rings around them. And it turns out that millions of years ago, another planet may have also had a ring: Mars.
New research published this week in the journal Nature Geosciences, suggests that one of Mars’ moons, Phobos, may be locked in a cycle where, over millions of years, it alternates between a ring of debris encircling the planet and a moon formed from that coalesced material.
Phobos is a small, pockmarked body that orbits about 3,700 miles above the surface of Mars—the closest orbit of any moon in the Solar System. But the gravity that keeps its celestial buddy nearby has also caused the tiny body stress, according to NASA. Phobos already has fractures on its surface and NASA estimates that it will be torn to shreds within 30 to 50 million years.
In the new study, researchers used computer modeling to examine Phobos' past and predict its future. The researchers suggest that an asteroid or other celestial body slammed into mars 4.3 billion years ago—an impact that created a massive basin on the planet's surface. This latest study, however, suggests that rather than creating the moons, the impact first sent debris shooting out into orbit around the planet. Eventually, that rocky debris ring coalesced into a large, lumpy moon.
Over time, Mars' gravity pulled that lumpy planetoid closer, bringing it within the so-called Roche Limit, or the distance at which a smaller body can exist as a self-contained unit under its own gravity. Any closer and the larger body's gravity rips the little moon apart.
When Mars' moon reached the Roche Limit in the past, it went from moon to ring. But again, over tens of millions of years, that debris clumped back together into a moon.
The simulation suggests that Phobos’ first iteration was likely a fairly large moon, reports Ryan F. Mandelbaum at Gizmodo. But over the last 4.3 billion years, it went through the ring-moon cycling three to seven times—each time losing a bit of mass to rocks that rain down on mars. The next time the moon crumbles, the model estimates it will lose another 80 percent of its mass. About 70 million years later, it will form another, much smaller Phobos version 8.0 (or so).
While the idea is compelling, it’s not the only proposal for the origin of Mars' moons. It does, however, offer something concrete for researchers to look for on the surface of mars: piles or layers of moon rocks from past moon explosions, according to a press release.
What about the other moon? As Mandelbaum explains, Deimos is outside the point where Mars' graity draws it in and could drift further and further away from the red planet, possibly escaping in the future.
The researchers plan to continue their work by looking deeper into the original ring around Mars or to try and investigate the potential sediment on the Martian surface.
|
Click here to Reply or Forward
|
Subscribe to:
Posts (Atom)