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.

Liquid Water on Pluto?

Prior to 2015, scientists knew little about Pluto, mainly because it is dim and small from Earth’s perspective, not to mention 4.67 billion miles away.

When NASA’s New Horizons space probe flew by the far-away dwarf planet, imaging it in unprecedented detail, the historic mission raised more questions than answers. For one, the probe’s findings raised suspicions that some of Pluto’s mountains were formed on a bedrock of water ice.

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According to a new study, computer simulations provide have provided compelling evidence that an insulating layer near the surface is keeping a subsurface ocean from freezing beneath Pluto’s ice. In other words, there could be a liquid ocean on the planet.

A team of Japanese scientists published the study, proposing that such an otherworldly idea is possible because a thin layer of ice containing trapped gas molecules, known as gas hydrates, at the bottom of the ice shell could be insulating the ocean.  By calculating Pluto’s temperature and the thickness of the ice shell, the scientists concluded that the gas hydrates would be enough to maintain a subsurface ocean.

Understanding how a subsurface ocean can exist on Pluto will provide scientists with invaluable information to better understand how similar bodies of water can exist on other planets, too. Liquid water oceans are thought to exist inside icy satellites of gas giants such as Europa and Enceladus. Understanding the survival of subsurface oceans is of fundamental importance not only to planetary science but also to astrobiology.

Scientists have been repeatedly surprised and bewildered by the data New Horizons collected and processed from its flyby in 2015. Even the initial photos showed unexpected complexity of the dwarf planet.

The study is published in in the journal Nature Geoscience.

Old Scars on Mars

Mars is a cold, dry place, but it may not always have been. Recent studies increasingly indicate that the planet once had a thicker, denser atmosphere that was able to lock in far more warmth, and therefore facilitate and support the flow of liquid water on the surface.

While this is no longer the case, planetary researchers have seen clear signs of past water activity across the Martian surface. New images from ESA’s Mars Express orbiter show one such region: a branching system of trenches and valleys in the southern highlands of Mars.

The southern highlands are some of the oldest and most heavily cratered parts of the planet, with many signs of ancient water. The topography of this region suggests that water flowed downhill from the north to the south, carving out valleys up to 1.2 miles (2 km) across and 656 feet (200 m) deep as it did so.

It is thought that climate change took place on Mars 3.7 to 3.8 billion years ago, when environmental conditions changed from a somewhat neutral, potentially life-sustaining and humid environment to a much drier, colder environment that is hostile to life.

One of the reasons why Mars lost its atmosphere was the loss of its magnetic field, which was active during its first 500 million years.

As the magnetic field grew weaker the solar wind was able to gradually split the molecules in the atmosphere. The resultant ions were then lost to space. As a result, and also due to declining volcanism, the atmosphere became thinner. Below a certain atmospheric pressure, water can no longer remain liquid on the surface of a planet, it can only remain as ice or gas.

Mars is also only about half the mass of Earth, so its gravitational force is barely sufficient to bind atmospheric molecules to it and the lack of precipitation on Mars collapsed the water cycle.

While it is unclear where all of this water came from originally (precipitation, groundwater, melting glaciers) all of this required a far warmer and more watery past for Mars.