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Monthly Archives: July 2016

From a report in the New York Times by Nicholas St Fleur:

Continents cruise in the slow lane. Moving just millimeters at a time, it took the ancient supercontinent Pangea hundreds of millions of years to break apart into today’s landmasses. But a study published Tuesday shows that the journey wasn’t always a leisurely drive. When under extreme strain, the tectonic plates hit the throttle and accelerated to speeds 20 times faster than they were traveling before.

22TB-Continental-master768

Credit: Sascha Brune

After analyzing seismic data from across the world and building a model, a team of geophysicists have discovered that plates move in two distinct phases: a slow phase and a fast one. During the slow phase, the continental crusts, which can be more than 20 miles thick, are stretched out little by little while remaining connected. But then suddenly, one or both of the continents step on the gas pedal. A critical point is reached when the connection between the two continents becomes so weak it can no longer resist the forces trying to pull it apart. This acceleration is directly related to the thinning of the crust.

Links: NYT article; computer simulation illustrating the movement of different continents.

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From JPL press releases, July 4, 2016:

While Americans celebrated the evening of Independence Day, 1.7 billion miles (2.7 billion kilometres) NASA’s Juno spacecraft, launched nearly five years ago, reached its final destination: the most massive planet in our Solar System, Jupiter.

juno_burn

Credit: NASA/JPL-Caltech

Juno now starts its tour of Jupiter in a 53.5-day orbit. The spacecraft saves fuel by executing a burn that places it in a capture orbit with a 53.5-day orbit instead of going directly for the 14-day orbit that will occur during the mission’s primary science collection period. The 14-day science orbit phase will begin after the final burn of the mission for Juno’s main engine on October 19.

Most of Juno’s instruments deal with Jupiter’s particles and magnetic field, which is 20,000 times more powerful than Earth’s. The main instruments are in a vault made of 400 pounds of titanium to protect them from the strong radiation. The Junocam, its imaging camera, is outside that protection, and may not last as long as other instruments; further, it will give images as it rotates that will have to be transformed to the equivalent of steady views.

Links: Full details via the JPL press release; NASA Juno mission page; NY Times: Jupiter and its moons graphic.

A report published on June 30, 2016, in the journal Science indicates that the hole in the ozone layer above Antarctica shows signs of beginning to heal. Since its discovery in 1985 the ozone hole has grown bigger each Spring, reaching a size of 10.9 million square miles in 2015.

The main cause of the hole is man-made chemicals known as CFCs (chlorofluorocarbons), which were widely used as propellants, refrigerants and solvents until they were banned by an international treatment in 1987 – use of CFCs had to be phased out by 1996. However, CFCs in the atmosphere are long-lived, so it will be decades, possibly centuries, before the ozone layer can fully repair itself. Naturally-released sulphur gases, for example, from volcanic eruptions can also affect the ozone layer, acting to slow its recovery.

Links: LA Times article; Science news feature and video.

On June 15, 2016, scientists at LIGO announced they had detected a second pair of black holes merging, at a distance of 1.4 billion light years, releasing the energy equivalent of the mass of the Sun. The consequent ripples in space-time shook the twin detectors at LIGO on December 26, 2015.

This brings the number of confirmed detections by LIGO to two within just four months, giving scientists optimism that more events will follow, enabling quantitative predictions about how frequently these high-energy events occur across space and time.

Read more in this NYT article, including a short video.