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02/18/2020: The moon will 'eclipse' Mars before dawn Tuesday! Here's how to see it.
As the waning crescent moon rises in the small hours of the morning of Tuesday, Feb. 18, skywatchers will be preparing for an unusual event. That morning the moon glides in front of orange, starlike planet Mars for viewers in much of central and eastern North America, in what is known as an occultation.
Parts of the western and central U.S. and Canada will be able to view both the disappearance and reappearance of the Red Planet in a dark or twilight sky. However, from western Canada, the Pacific Northwest and northern portions of California and Nevada, only the end of the occultation will be seen, since Mars will already be behind the moon when it rises around 3:30 a.m. local time. On the other hand, across the Eastern U.S., the planet will both disappear and emerge after sunup.
Under reasonably dark skies, this event can be watched over western locations with the naked eye or binoculars, although a telescope will provide the best views. Over the Desert Southwest and parts of the Rocky Mountain States along and east of the Continental Divide, the entire event will occur under a dark sky, but will take place very low in the east-southeast; an open view of the horizon is required. Right now, Mars is relatively faint at magnitude +1.2 and will be dimmed further by its low altitude, but it should not be hard to spot.
Near and immediately east (right) of a line extending roughly from Santa Barbara, California to Idaho Falls, Idaho to Havre, Montana, the bright limb of the moon occults the planet when it is still too low to view. But Mars' reappearance from behind the moon's dark limb will be much more observable, because the moon will be higher above the horizon and the planet won't be washed out by the crescent's bright glare.
Unlike the pinpoint image of a star, which upon interaction with the moon appears to vanish or reappear as if you've clicked a switch, the larger apparent size of Mars causes it to disappear or emerge more gradually. About 15 seconds should elapse for the moon to fully cover (or uncover) the tiny disk of Mars after the edges of the two bodies appear to make contact. But the duration will be slightly longer for locations well to the north or south, where the occultation is not nearly central.
Mars currently shows a gibbous disk with an apparent diameter of 5.1 arc seconds. The first speck of light from the Red Planet when it reappears from behind the moon will be at the moon's dark limb and can be spotted by an observer looking in the right place with a small telescope. Mars will emerge into view as a tiny, brilliant fiery blob — seemingly like a burst of lava from some great lunar volcano.
In order to help observers anticipate where Mars will disappear (behind the moon's bright limb) and reappear (from behind the moon's dark limb), the accompanying diagram shows the apparent path of Mars as seen from various cities. The numbers specify the cities as given in this list. For some locations (such as San Francisco, #17), the disappearance will occur before moonrise, so its track on the left is not shown.
More difficult farther east
As one heads east, the occultation will take place after the break of dawn and the advance of morning twilight. Across the northern and central Great Plains, as well as the western half of Oklahoma and Texas, Mars will disappear in a dark sky, but twilight will be well advanced when it reappears. Binoculars or a telescope will be needed to see the emergence from behind the moon's dark limb. From the Great Lakes, Greater Ohio Valley and the Deep South, Mars will disappear in a twilight sky and reappear after sunrise.
And for New England, upstate New York, Toronto and Montreal, the greater New York City area and New Jersey, Middle Atlantic Coast, Piedmont and Southeast Coast including Florida, the entire occultation will be a daytime affair.
Trying to see the occultation from these regions will prove to be quite a challenge to say the least!
Prior to sunrise, you'll see Mars sitting less than a couple of degrees to the left of the 24% illuminated lunar crescent. Moving at roughly its own apparent diameter per hour, the moon will appear to gradually creep closer to Mars as they slowly ascend and the background sky turns progressively brighter. With the naked eye alone, you'll probably lose sight of Mars about a half hour before sunrise, though it still should be readily visible through binoculars and small telescopes. To continue seeing it after sunrise however, will require a very clear (haze-free) day. The surface brightness of Mars (amount of light per square arc second) is about equal to that of the moon.
In the accompanying table, predicted times at 28 cities are given for this "Mars eclipse." Also included is whether the event in question takes place in a dark sky, at mid-twilight (30 to 60 minutes before sunrise), bright twilight (30 minutes to just a few minutes before sunrise), near sunrise (within a couple of minutes of sunup) and daytime (after sunrise).
For San Francisco and Seattle, where no time is listed under disappearance, that event occurs before moonrise.
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**NASA's InSight Mars Lander 'Hears' Martian Wind, a Cosmic First**
For the first time in history, we can hear the wind on Mars. Well, sort of.
NASA's InSight lander touched down on the Red Planet Nov. 26, and since its arrival, the robot has focused on acclimating to its new environment on Elysium Planitia. And now, the team behind the mission has turned the first bits of that data into an incredible new soundtrack, which you can hear in a new video, released today (Dec. 7).
"This is the first time on the surface of Mars that we've had instruments that can detect up to the frequency that humans can hear," Tom Pike, a scientist on the InSight project who focuses on the sensors, said during a news conference unveiling the recording.
But while the instruments on InSight can capture data in human-friendly frequencies, higher-pitched sounds don't travel well on Mars. So, NASA also provided a version of the recording shifted up in pitch, which pulls some of the otherwise-inaudible infrasound into hearing range.
That's because the instruments weren't shipped all that way to become interplanetary rock stars. Instead, they're specially designed to tackle an important scientific challenge: solving mysteries about the interior of Mars.
To get high-quality data from the incredibly sensitive seismometer onboard the lander, the team needs to be able to cancel out all the commotion coming from the Martian surface, looking only at signals coming from inside the planet. Because wind gusts can trick the seismometer, the lander is equipped with an air pressure sensor to isolate that background noise.
"We're trying to design a noise-cancellation headphone system for our seismometer," InSight principal investigator Bruce Banerdt said.
But for InSight's first mixtape, none of the lander's instruments have been deployed. The new recording uses data from two sources, the air pressure sensor and the seismometer, which are both still on the instrument deck. That means they are well-placed to capture noises around and onboard the lander, including the sound of the wind blowing across InSight's solar arrays.
"Humans are multisensor people, and now we have two of our sensors turned on with this mission," with both audio and visual data streaming back to Earth, Don Banfield, the science lead for the air pressure sensor, said during the news conference.
The wind you hear in this recording is blowing at between 10 and 15 mph (5 to 7 meters per second) and originates from northwest of the lander, the scientists reported. The sample includes data gathered during the first 15 minutes that the sensors were recording. (Shifting noises to higher frequencies also plays recordings faster, so the clip is essentially a time lapse.)
"To me, the sounds are really unworldly," Banerdt said. "They do sound like the wind or maybe the ocean roaring in the background, but it also has kind of an unworldly feel to it."
But the scientists warned not to get too attached to these recordings, because they won't last long. The team is itching to deploy the seismometer and its protective cover, with the air pressure sensor nestled inside of that shield. When InSight is conducting its science mission, the seismometer won't be able to hear the wind, attuned only to the grumblings of the planet's interior.
The air pressure sensor inside the shield will be relocated as well, and the team will gather data at night, when it expects the wind will have died down and the lander itself will be making less noise. "What you're hearing now should get a lot quieter," Pike said. "It's going to become very difficult to hear the sounds from the outside of Mars later on."
In the meantime, the sounds of the Martian wind are a poignant reminder of just how far InSight has flown: more than 300 million miles (480 million kilometers), becoming only the eighth spacecraft to successfully touch down on the Red Planet.
"It's a really distant rumble that we're hearing," Pike said. "It just gives another way of thinking about how far away [we z6are when] we're getting these signals.
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Researchers in the Department of Earth, Atmospheric and Planetary Sciences will help direct Mars 2020 rover sample acquisition.
Planetary scientists believe that Mars was once warmer, had a significant atmosphere, and maintained abundant flowing water that carved out river channels and pooled in lakes. These conditions would, at least theoretically, support life. But following a July 2020 launch, a 34 million mile journey, and an elaborately choreographed descent though the scant Martian atmosphere, NASA’s Mars 2020 rover will encounter an entirely different world. Freezing. Dry. And with an atmosphere so thin that even if the temperature warmed enough to melt the polar ice caps, the water would immediately evaporate.
What happened to Mars? And did life ever exist on our dusty, red neighbor?
To investigate this Martian mystery, the Mars 2020 rover will collect cores of sediments and rocks that will be sealed in tubes and eventually brought to Earth. Once they’ve arrived, the cores can be analyzed with the same instruments and techniques researchers use to understand the deep history of Earth. However, the samples must be chosen strategically because only about three dozen can be brought back — not very many for researchers attempting to characterize the biological and geological history of an entire planet.
Associate professor of geobiology Tanja Bosak and professor of planetary sciences Ben Weiss, both in the MIT Department of Earth, Atmospheric and Planetary Sciences (EAPS), have been selected as participating scientists on the mission. They will be among the group of 10 people who will decide which samples to collect. Bosak has also been selected for an additional leadership position as a member of the Project Science Group, which outlines mission strategies and coordinates the different groups of scientists involved with Mars 2020.
Looking for Martian fossils
Bosak, an expert in fossilization processes, says that looking for signs of ancient life on Mars is especially challenging, because “if there was any life, it would have been microbial. [What] we need to do is to look for something microscopic.” Fossil relics of any kind are rare compared to the original population, and soft-bodied, microbial fossils are even more exceptional. Given this, “we need to look for life in environments where that life would have been abundant and likely to be preserved,” she says.
Planetary scientists suspect past life would have been abundant near water, which informed their choice to send the rover to Jezero crater, believed to be the site of an ancient lake. Satellite images suggest that the lake was fed by a river, which deposited sediments in a delta at its mouth. Cameras and portable analytical instruments on the rover will help the researchers acquire compositional data about these sediments before they decide to take a precious core sample. Bosak plans to use these tools to search for deposits of carbonate, clay minerals, and amorphous silica. These substrates or their analogs are known to preserve microbial structures or fossils on Earth.
Once the researchers have located interesting sediments, they can use the rover’s drill to dig in a bit, and a camera to look inside. On Earth, microbial fossilization processes can create visible formations in sediments that can’t be duplicated by abiotic geological processes. If the rover peers into a drill hole and sees this type of formation, it would be very compelling evidence of past life on Mars. However, researchers may have to wait until the samples can be scrutinized with more sophisticated technology back on Earth to see if they’ve found signs of life or chemical precursors of life.
Martian magnetism
If there is a story of life on Mars, there may also be a story of death — the catastrophic loss of an atmosphere, and potentially with it, a temperate environment and liquid water.
“The big question is, why did Mars go from being warm and wet to cold and dry,” says Weiss, a planetary geophysicist. “One of the leading ideas is that it lost its atmosphere.” If Mars lost a once-stable atmosphere, there would no longer be a greenhouse effect to keep the planet warm, or the atmospheric pressure necessary to keep liquid water from boiling. But what could have happened to the atmosphere?
“The hypothesis is that Mars lost its magnetic field and then the atmosphere was stripped away,” says Weiss. Planetary magnetic fields are generated by the churning of molten metals in the planet’s core. The field repels and redirects charged radiation from the sun that would otherwise destructively react with molecules in the atmosphere. If the Martian atmosphere was destroyed by unmediated solar radiation after losing its magnetic field, evidence of this event may be found inside Martian rocks.
When a rock is forming on a planet with a magnetic field, the electrons in the atoms that make up the rock will align themselves to the magnetic field. The stronger the planet’s magnetism, the more electrons in the rock will align themselves to it. Without a magnetic field, electrons orient randomly.
By acquiring a series of rock samples ranging in age from the very old to very young, and determining the proportion of aligned electrons in each sample, researchers could potentially track the disappearance of the Martian magnetic field. Weiss says that this timeline could then be compared to the record of climate change on Mars to see if loss of the magnetic field did, in fact, precede cooling and loss of water.
Scientific consensus
While Bosak and Weiss approach the Martian mystery from different angles, they and the other participating scientists will strive to ensure that each sample they collect will be useful to scientists across disciplines. “These 30 or so samples basically have to be shared [by] all of humanity. So, our job is not to just represent our own particular interests, but to represent the entire community today and conceive of what future generations might want,” says Weiss. “It's going to be a big, long debate every time we take any sample.”
Finding evidence of past life on Mars would be a remarkable discovery, but Bosak points out that there would still be a lot to learn about life even if Mars is completely sterile. “Mars is very similar to us in the sense that it did have liquid water. If we see that everything [on Mars] is sterile, that really does invite a whole bunch of questions about why it’s sterile,” she says. “What was not quite right for life? Or, if you find some evidence for prebiotic chemistry or something, [but not evidence of] cellular life, what made it stop?” Either way, “this is a really super exciting opportunity to get some answers.”
JPL built and will manage operations of the Mars 2020 rover for NASA’s Science Mission Directorate. NASA's Launch Services Program, based at the agency's Kennedy Space Center in Florida, is responsible for launch management.
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