New Horizons’ observations confirmed the light scattering and presence of hydrogen atoms, described by researchers who published the results in the August 7, 2018 edition of Geophysical Research Letters.

The researchers describe interplanetary medium atomic hydrogen observations as Lyman‐α emissions, a Lyman‐α, “a possible signature of the hydrogen wall at the heliopause,” the boundary that defines the edge of local space and the beginning of interstellar space.

Determining the size and shape of this hydrogen wall is helping astronomers to define the ultimate shape of the heliosphere, the bubble that surrounds our Solar System. Is the bubble spherical or elliptical in shape with a long magnetosphere-like tail? That remains unknown. When Cassini was orbiting Saturn, the instrumentation on board was able to image the heliosphere of our Solar System over eleven years of observation. At the time it suggested a more spherical shape (see image below) and not one similar to the magnetosphere that surrounds Earth with its long comet-like tail.

The New Horizons data which continues to come in as it travels through the Kuiper Belt on its way to exit the Solar System, provides much more sensitive readings than either Cassini or the two Voyagers. It already has scanned the ultraviolet sky seven times from 2007 to 2017, and should over the next fifteen to twenty years, the estimated operational life of the robotic spacecraft, provide a far more detailed view of the hydrogen wall and its dimensions. If it notes, at some point, a drop off in the ultraviolet spectrum, it may mean New Horizons has passed through the hydrogen wall. Current observations suggest a distance of at least 100 times further out than Earth is to the Sun.

What they report in their paper is, that polar ice sheets exert a gravitational pull on the water to which they are adjacent. That these slight pulls make sea levels higher at the intersection point where ice meets ocean. So as a glacier loses mass the pull weakens causing adjacent sea levels to fall. And as ice mass decreases, the land underneath it experiences isostatic rebound.

What is isostatic rebound?

It is the rise in elevation of continental land masses following melting of glaciers and ice sheets lying on top of them. Once the weight of the ice is gone, the land literally bobs back up. That rebound further lowers sea levels adjacent to the land where the ice mass melts. The combination of melt and rebound alters Earth’s gravitational field causing the extra volume of water to migrate far from its points of origin. For example, the researchers note that Antarctic ice melt correlates to a 52% faster rate of sea level rise off California and Florida than elsewhere on the planet.

Velicogna, the lead scientist of the paper, notes that lower latitudes exhibit the highest sea level rise because of gravitational field changes. The data that supports this comes from NASA’s GRACE satellites which measure gravitational changes on the Earth’s surface. Covering 12 years, from 2002 to 2014, scientists analyzed GRACE findings and then correlated them to other measurement sources including pressure stations on the ocean floor. The latter measure the mass of water above their locations and therefore give an accurate vertical height of the ocean surface.

What are the implications of this research?

Since sea level rise is variable across the planet it is important that scientists measure as many points as possible to understand the implications of further ice melts from Antarctic, Greenland and the Canadian Northern Archipelago. There should be a call for the widespread deployment of ocean floor pressure stations feeding continuous measurements so that we have a better picture of which coastlines will be most impacted by these gravitational shifts. For example, we know that the northern parts of North America and Siberia are still experiencing isostatic rebound from the last Ice Age, more than ten thousand years after the ice retreated. Geology and geological time move slowly.

Another phenomenon complicates issues further. Those northern areas of the hemisphere that rebound cause areas of the continent adjacent to them to be impacted in reverse. For example, the subsidence of The Chesapeake Bay area and Florida is in part because of continental rebound experienced to the north.

Global Thermal Expansion and Weather Phenomena

Back in August, I wrote about another paper appearing in Geophysical Research Letters that described sea level rise three times faster on the Eastern Seaboard of the United States than the global average. The paper’s authors argued that two phenomena, the North Atlantic Oscillation combined with an El Nino were the contributing factors to this accelerated rise.

Add to this thermal expansion, a phenomenon caused by density decreases in water when it is heated causing it to expand. Ocean water columns are showing increased warming throughout. This phenomenon is contributing to sea level rise, but to what extent, remains an unknown. represents an additional threat to coastlines, particularly during high tides and storm surges.

For cities like Miami and Miami Beach, the combination of all of these phenomena, glacial ice melt, gravitational shifts, isostatic rebound, confluences of weather phenomena, and thermal expansion, represent the reasons why there are increasingly frequent sunny-day flooding events in these communities.

Discovering a water mass that large on Mars, therefore, can be considered a big deal.

It is not the first water to be found on the planet. The Viking 2 landed in the locale of the ice mass discovery but it didn’t have instrumentation to do a scan of the geology beneath. What it did do, however, is send us the first pictures ever seen by humans of Martian ground frost (see picture below).

Phoenix took pictures of condensed water on one of its surfaces (see three images below), and uncovered ice that when exposed to Martian air evaporated.

And Mars sports two polar ice caps (the northern one can be seen in the picture below) approximately 3 kilometers thick containing enough water to cover the entire planet to a depth of 5.6 meters (18 feet).

So what’s the fuss?

The water the Mars Reconnaissance Orbiter discovered using its ground-penetrating SHARAD radar is buried under Utopia Planitia, “Plains of Paradise” at a latitude between 39 and 49 degrees north. It is in the form of ice and varies in thickness from 79 and 171 meters (260 to 560 feet). The overlay varies from 1 to 10 meters (3.3 to 33 feet) in thickness making it easy to access. Far more hospitable and accessible than the polar ice caps, human visitors to Mars could turn this discovery into a critical resource.

The volume of water stored underground is twice as large as any other known buried ice sheets on the northern half of the planet and is close enough to the surface to be tapped. Spectographic analysis shows that it is betweeen 50 and 85% water ice with the remainder dust and mixed solids. The location is an area that is relatively flat making it a suitable place for a spaceship to touch down.

The ice can serve a human team of explorers in many ways. It can be a source of freshwater. Oxygen can be extracted from it. And hydrogen for making rocket fuel or for fuel cells.

Sampling the ice by drilling ice cores will give us a much better picture of Mars’ geological history. At the same time there may be life hibernating or active within the ice.

The discovery was reported in the journal  Geophysical Research Letters. Lead author, Cassie Stuurman, Institute for Geophysics, University of Texas, Austin, speculates on the origin of the ice. “This deposit probably formed as snowfall accumulating into an ice sheet mixed with dust during a period in Mars history when the planet’s axis was more tilted than it is today.”

Mars today has an axial tilt of 25.1 degrees, about 2 degrees more than Earth’s. But unlike Earth which has only a small axial wobble, about every 120,000 years Mars tiltsas much as twice 25 degrees. With a 50 degree tilt the polar ice caps heat up and melt and moisture condenses out to form ice at middle latitudes. The speculation is the frozen mass formed during one of those high-tilt periods.

In the study the researchers simulated islands in the southern part of The Bahamas which get almost all of their freshwater from precipation. They noted that as sea levels rise so did groundwater causing surface lakes to expand and new ones to form. This sped up evaporation.

Shannon Sterling of Dalhousie University in Halifax, Nova Scotia, is not one of the authors of the research. She notes that the consequences for islands could ve severe stating, “this new mechanism will affect large areas of the planet or have measurable changes to the global water budget, but because reductions in available water are occurring in already water-limited sensitive areas, with potentially large economic and human consequences.”

The study could have implications for more than islands. Rising sea levels are introducing saltwater into freshwater aquifers in places like Florida. Florida has spent billions of dollars to stop the phenomenon from contaminating drinking water and water used for industrial and agricultural purposes. The South Florida Water Management District has installed reverse osmosis plants to convert brackish water that has intruded into the deep water aquifer.

In addition rainwater conservation mechanisms have been put in place to ensure adequate freshwater supplies for this part of Florida which is home to significant urban growth. Areas most impacted are Miami-Dade County where low elevations and rising sea levels are causing saltwater creep in the aquifer. The state has implemented a $4.1 billion potable water plan to fight what scientists believe will be a growing challenge as climate change impacts sea levels.

States Barry Heimlich, a retired engineer with a background in the petroleum and pharmaceutical industries, “As the sea level rises, saltwater pushes inland like a parabolic curve – the deeper you go the more saltwater there is and it moves inland…..some wells have become contaminated and were moved inland and that will probably continue. Even a small amount of sea rise can have a very large effect.”