Ice, Ice, Baby

 

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Planetary researchers using data from the Shallow Radar (SHARAD) instrument on NASA’s Mars Reconnaissance Orbiter have discovered rich deposits of water ice and sand hundreds of million years old beneath the current ice cap in the north polar region of the Red Planet. Published journal Geophysical Research Letters, the findings are important because the layers of ice are a record of past Martian climate in much the same way that tree rings are a record of past climate on Earth.

Scientists found layers of sand and ice that were as much as 90% water in some places. If melted, the newly-discovered ice would be equivalent to a global layer of water around Mars at least 5 feet (1.5 m) deep, which could be one of the largest water reservoirs on the planet.

The scientists suspect the layers formed when ice accumulated at the poles during past ice ages on Mars. Each time the planet warmed, a remnant of the ice caps became covered by sand, which protected the ice from solar radiation and prevented it from dissipating into the atmosphere.

Until now, scientists thought the ancient ice caps were lost. The new findings show that in fact significant ice sheet remnants have survived under the planet’s surface, trapped in alternating bands of ice and sand, like layers on a cake.

The total volume of water locked up in the buried polar deposits is roughly the same as all the water ice known to exist in glaciers and buried ice layers at lower latitudes on Mars, and they are approximately the same age.

The team’s findings were corroborated by an independent study using gravity data instead of radar, led by Johns Hopkins University’s Dr. Lujendra Ojha and also published in the journal Geophysical Research Letters.

Moonshots

Last month, NASA’s Mars Odyssey orbiter captured a new thermal image of Phobos, the larger of Mars’ two moons. Each color in the full-moon image represents a temperature range detected by Odyssey’s Thermal Emission Imaging System (THEMIS) camera. Each observation is done from a slightly different angle or time of day, providing new kinds of data.

The new, full-moon view is better for studying material composition, whereas earlier half-moon views are better for looking at surface textures. With the half-moon views, scientists could see how rough or smooth the surface is and how it’s layered. With the new full-moon views, scientists can gather data on what minerals are in it, including metals.

These three views of the Martian moon Phobos were taken by NASA’s Mars Odyssey orbiter using its THEMIS camera. Each color represents a different temperature range. The upper image was taken in a full-moon phase, which is better for studying material composition. The two views below were taken while Phobos was in a half-moon phase, which is better for studying surface textures. Image credit: NASA / JPL-Caltech / ASU / SSI.

Iron and nickel are two such metals. Depending on how abundant the metals are, and how they’re mixed with other minerals, researchers might be able to determine whether Phobos is a captured asteroid or a pile of Mars fragments blasted into space by a giant impact long ago.

Human exploration of Phobos has been discussed in the space community as a distant, future possibility, and a Japanese sample-return mission to the tiny moon is scheduled for launch in the 2020s. These and future observations could help future missions identify hazards and find safe areas to land of the surface.

Rise and Fall…On Mars

In April 2019, NASA’s InSight lander used its Instrument Deployment Camera (IDC) to capture a series of Martian sunrise and sunset images.

NASA’s InSight lander used its IDC camera to record the Martian sunrise on April 24, 2019. This image was taken around 5:30 a.m. Mars local time. Image credit: NASA / JPL-Caltech.

The first mission to send back such images was NASA’s Viking 1 lander, which captured a sunset on August 21, 1976. NASA’s Viking 2 then captured a sunrise on June 14, 1978. Since then, both sunrises and sunsets have been recorded by NASA’s Spirit, Opportunity and Curiosity rovers.

InSight’s IDC camera on the lander’s robotic arm snapped these photos on April 24 and 25, 2019, the 145th Martian day (sol) of the mission. In local Mars time, the shots were taken starting around 5:30 a.m. and then again starting around 6:30 p.m.

Much farther from Mars than it is from Earth, the Sun appears only about two-thirds the size that it does when viewed from Earth.

InSight used its IDC camera to image this sunset on Mars on April 25, 2019. This image was taken around 6:30 p.m. Mars local time. Image credit: NASA / JPL-Caltech.

Marsquakes

NASA’s robotic probe InSight detected and measured what scientists believe to be a “marsquake,” marking the first time a seismological tremor has been recorded on another planet, the Jet Propulsion Laboratory in California reported on Tuesday.

The breakthrough came nearly five months after InSight, the first spacecraft designed specifically to study the interior of a distant world, touched down on the surface of Mars to begin its two-year seismological mission on the red planet.

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The faint rumble was roughly equal to a 2.5 magnitude earthquake, was recorded on April 6, the lander’s 128th Martian day, or sol.

It was detected by InSight’s French-built seismometer, an instrument sensitive enough to measure a seismic wave just one-half the radius of a hydrogen atom.

Scientists are still examining the data to conclusively determine the precise cause of the signal, but the trembling appeared to have originated from inside the planet, as opposed to being caused by forces above the surface, such as wind.

The size and duration of the marsquake also fit the profile of some of the thousands of moonquakes detected on the lunar surface between 1969 and 1977 by seismometers installed there by NASA’s Apollo missions.

The lunar and Martian surfaces are extremely quiet compared with Earth’s, which experiences constant low-level seismic noise from oceans and weather as well as quakes that occur along subterranean fault lines created by shifting tectonic plates in the planet’s crust.

Curiosity Catches Two Eclipses

The cameras on NASA’s Curiosity rover usually look down at the rocks on Mars, divining clues in the minerals of what the planet was like billions of years ago.

Sometimes though, the rover also looks up, and in March it spotted two eclipses (eclipsi?).

Eclipses on Mars are not as total as those on Earth where the moon completely blots out the sun. The two moons of Mars are tiny. Phobos is 7 miles wide while Deimos is even tinier, just 1.5 miles in diameter. They only partially block the sun when they pass in front of it.

The camera on Curiosity’s mast is equipped with solar filters that allow it to look directly at the sun and photograph eclipses. On March 17, Curiosity observed Demios eclipsing the sun. Nine days later, it also spotted Phobos passing in front.

The observations by Curiosity, and by earlier NASA Mars rovers, Spirit and Opportunity, enable more precise pinpointing of the moons’ orbits, which are jostled around by the gravity of Mars, Jupiter, and even each other.

Although Phobos and Deimos are small, the details of their formation are of considerable scientific interest. Japan’s space agency plans to send a spacecraft to the two moons within the next decade. The Mars Moon Exploration probe, or MMX, will collect samples and return them to Earth for study. A panel of scientific experts recently approved the sample-return phase of the mission.