April 2016 - Page 3 of 4 - The Spacewriter's Ramblings

Exploring the Deeps of the Solar System

I gotta say: we live in a time of fascinating scientific discoveries in our solar system. We’ve been in a “golden age” of in situ planetary exploration that began in the 1960s. Now, well into the 21st century, space agencies around the world continue to dish out juicy findings. Every week I see news from the outer solar system in the form of Pluto and Charon system results from the New Horizons mission. We’re also getting frequent updates from the Dawn mission currently circling Ceres, a dwarf planet out beyond the orbit of Mars in the Asteroid Belt. I find it amazing that we can know so much about these distant places, all through the efforts of a two small spacecraft and the science teams that built and continue to manage them.

Visiting Ceres

For example, Dawn has been in “deep orbit” around Ceres. Since 2015, it has been snapping up high-resolution images and data of the surface. The team just released an image of Haulani crater, a 21 mile-wide impact feature that seems to show evidence of landslides from its crater walls. This enhanced-color image shows the younger features in blue and older ones in gray. The rays extending out around the crater (and colored blue) are made of material ejected as something slammed into the Cerean surface. It also looks like whatever smacked Ceres hit this world right in a region that was already stressed and fractured. Hence the odd shape of the crater.

The Dawn mission is continuing to explore Ceres in minute detail, giving us new insight into this frozen, cracked, and cratered world.

Pluto’s Latest and Greatest

This image of Pluto's spider terrain was obtained by New Horizons’ Ralph/Multispectral Visible Imaging Camera (MVIC). It was obtained at a range of approximately 21,100 miles (33,900 kilometers) from Pluto, about 45 minutes before New Horizons’ closest approach on July 14, 2015. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute — This image of Pluto’s spider terrain was obtained by *New Horizons*’ Ralph/Multispectral Visible Imaging Camera (MVIC). It was obtained at a range of approximately 21,100 miles (33,900 kilometers) from Pluto, about 45 minutes before New Horizons’ closest approach on July 14, 2015. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

While New Horizons is no longer at Pluto, it continues to radio back data across the solar system from its momentous 2015 encounter. Pluto continues to amaze everybody with a wide range of interesting features in its icy crust. The latest up-close image shows a region of cracked terrain nicknamed the “Ice Spider” of Pluto. Nothing quite like it has been seen on other bodies in the outer solar system.

This crack in the crust is a set of fractures. The longest one is about 580 km (360 miles) long and appears to lie roughly north-south. The shorter cracks run east-west. They’re only about 100 km (60 miles) long. There’s also a hint of some kind of reddish material in some of the spider’s legs.

The fractures that make up the spider are probablye due to a global extension and shrinking of Pluto’s water-ice crust. However, they could also be telling us there’s some local activity occurring, too.

Award-Winning Science

Both the New Horizons and Dawn Mission teams have been winning prestigious awards for their work exploring these distant worlds. On March 8, the Dawn project team was chosen for the prestigious National Aeronautic Association Robert J. Collier Trophy “for the greatest achievement in aeronautics or astronautics in America, with respect to improving the performance, efficiency and safety of air or space vehicles, the value of which has been thoroughly demonstrated by actual use during the preceding year.” Established in 1911, the 8-foot tall trophy resides at the Smithsonian National Air and Space Museum in Washington and is engraved with the names of recipients. Dawn competed with a field of nine finalists to win this year’s award. The award will be presented on June 9.

On March 11, the team was also honored with the National Space Club and Foundation’s Nelson P. Jackson Award, presented annually for “a significant contribution to the missile, aircraft or space field.” The Dawn team accepted the award at the organization’s 59th Annual Robert H. Goddard Memorial Dinner in Washington.

New Horizons team members are also basking in the glory of their achievements. PI Alan Stern, who was just named one of Time magazine’s list of 100 most influential people in the world, accepted the Carl Sagan award earlier this year, and gave a Kavli Prize Lecture at the American Astronomical Society meeting about his team’s exploration of the outer solar system. The team itself has earned the John L. “Jack” Swigert, Jr. Award for Space Exploration from the Space Foundation, the National Space Society Space Pioneer Award, and many others. The Smithsonian Institution also gave the New Horizons team a Current Achievement award.

As these two missions continue on their voyages of discovery, I’m sure we’ll ALL be awarded with more great views and data of distant worlds.

Planets: Don’t Fly Too Close to Your Star

In the old legend of Icarus, the man-god flew too close to the Sun against his father’s warnings. The heat from our star melted his waxy wings and Icarus plummeted to his death. It’s a cautionary tale as old as humanity.

There’s a new variation on that myth, and it has to do with a subset of super-Earth exoplanets recently studied by astronomers. These are rocky worlds with atmospheres and they make tight orbits around their stars. Intense radiation from their parent stars simply blows away their atmospheres, leaving behind a barren wilderness of a planet.

This doesn’t happen to every massive planet and its star, but it may be something that happens as young stars and their newly formed planets evolve over time. The most likely candidates for this atmospheric stripping are worlds that received 650 times MORE radiation than Earth receives from the Sun. The planetary atmospheres don’t have a chance. They just get blown away — gone with the stellar wind.

Asteroseismology Tells the Tale

The astronomers who found these airless worlds used data from the Kepler mission to study the stars where these worlds orbit. The data helped researchers perform asterseismology to characterize the host stars, and to figure out the sizes of their super-Earth planets. The worlds without atmospheres turn out to be a new category of exoplanets, and occupy a niche in planetary formation and evolution that astronomers are still working to understand.

Asteroseismology is a technique that reveals the inner structure of a star. Astronomers use it to measure a star’s pulsations. Different rates of oscillations give clues to activity at several depths and the star’s surface. It’s not unlike studying seismic waves on Earth during earthquakes. In that case, geologists use the waves to understand the structure beneath of the surface of our planet.

A star’s oscillations are reflected in its brightness variations. Even the most subtle pulsations can tell something about the star, and finding planets barren of atmospheres orbiting distant stars gives a clue about past and current stellar activity. Asteroseismology helps complete that picture.

I’m constantly amazed at the things we learn about the cosmos using such tools as the Kepler telescope. What started out as a planet search is yielding amazing peeks into the interiors of stars, too.

The Spacewriter's Ramblings

Monthly Archives: April 2016

Pluto and Ceres: Solar System Gifts that Keep on Giving