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How the Sun Affects Asteroids in Our Neighborhood

It’s no secret the Sun affects us here on Earth in countless ways, from causing sunburns to helping our houseplants thrive. The Sun affects other objects in space, too, like asteroids! It can keep them in place. It can move them. And it can even shape them.

Asteroids embody the story of our solar system’s beginning. Jupiter’s Trojan asteroids, which orbit the Sun on the same path as the gas giant, are no exception. The Trojans are thought to be left over from the objects that eventually formed our planets, and studying them might offer clues about how the solar system came to be.

Over the next 12 years, NASA’s Lucy mission will visit eight asteroids—including seven Trojans— to help answer big questions about planet formation and the origins of our solar system. It will take the spacecraft about 3.5 years to reach its first destination.

How does the Sun affect what Lucy might find?

Place in Space

Credits: Astronomical Institute of CAS/Petr Scheirich

The Sun makes up 99.8% of the solar system’s mass and exerts a strong gravitational force as a result. In the case of the Trojan asteroids that Lucy will visit, their very location in space is dictated in part by the Sun’s gravity. They are clustered at two Lagrange points. These are locations where the gravitational forces of two massive objects—in this case the Sun and Jupiter—are balanced in such a way that smaller objects (like asteroids or satellites) stay put relative to the larger bodies. The Trojans lead and follow Jupiter in its orbit by 60° at Lagrange points L4 and L5.

Pushing Asteroids Around (with Light!)

The Sun can move and spin asteroids with light! Like many objects in space, asteroids rotate. At any given moment, the Sun-facing side of an asteroid absorbs sunlight while the dark side sheds energy as heat. When the heat escapes, it creates an infinitesimal amount of thrust, pushing the asteroid ever so slightly and altering its rotational rate. The Trojans are farther from the Sun than other asteroids we’ve studied before, and it remains to be seen how sunlight affects their movement.

Cracking the Surface (Also with Light!)

The Sun can break asteroids, too. Rocks expand as they warm and contract when they cool. This repeated fluctuation can cause them to crack. The phenomenon is more intense for objects without atmospheres, such as asteroids, where temperatures vary wildly. Therefore, even though the Trojans are farther from the Sun than rocks on Earth, they’ll likely show more signs of thermal fracturing.

Solar Wind-Swept

Like everything in our solar system, asteroids are battered by the solar wind, a steady stream of particles, magnetic fields, and radiation that flows from the Sun. For the most part, Earth’s magnetic field protects us from this bombardment. Without magnetic fields or atmospheres of their own, asteroids receive the brunt of the solar wind. When incoming particles strike an asteroid, they can kick some material off into space, changing the fundamental chemistry of what’s left behind.

Follow along with Lucy’s journey with NASA Solar System on Instagram, Facebook, and Twitter, and be sure to tune in for the launch at 5 a.m. EDT (09:00 UTC) on Saturday, Oct. 16 at nasa.gov/live.

Make sure to follow us on Tumblr for your regular dose of space!

Every next level of your life will demand a different you.

Leonardo DiCaprio (via quotemadness)

   Take time to think, it is the source of power. Take time to read, it is the foundation of wisdom.

Sea Level Rise is on the Rise

As our planet warms, sea levels are rising around the world – and are doing so at an accelerating rate. Currently, global sea level is rising about an eighth of an inch every year.

That may seem insignificant, but it’s 30% more than when NASA launched its first satellite mission to measure ocean heights in 1992 – less than 30 years ago. And people already feel the impacts, as seemingly small increments of sea level rise become big problems along coastlines worldwide.

Higher global temperatures cause our seas to rise, but how? And why are seas rising at a faster and faster rate? There are two main reasons: melting ice and warming waters.

 The Ice We See Is Getting Pretty Thin

About two-thirds of global sea level rise comes from melting glaciers and ice sheets, the vast expanses of ice that cover Antarctica and Greenland. In Greenland, most of that ice melt is caused by warmer air temperatures that melt the upper surface of ice sheets, and when giant chunks of ice crack off of the ends of glaciers, adding to the ocean.

In Antarctica – where temperatures stay low year-round – most of the ice loss happens at the edges of glaciers. Warmer ocean water and warmer air meet at the glaciers’ edges, eating away at the floating ice sheets there.

NASA can measure these changes from space. With data from the Ice, Cloud and land Elevation Satellite-2, or ICESat-2, scientists can measure the height of ice sheets to within a fraction of an inch. Since 2006, an average of 318 gigatons of ice per year has melted from Greenland and Antarctica’s ice sheets. To get a sense of how big that is: just one gigaton is enough to cover New York City’s Central Park in ice 1,000 feet deep – almost as tall as the Chrysler Building.

With the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission – a partnership with the German Research Centre for Geosciences – scientists can calculate the mass of ice lost from these vast expanses across Greenland and Antarctica.

It’s not just glaciers in Antarctica and Greenland that are melting, though. Nearly all glaciers have been melting in the last decade, including those in Alaska, High Mountain Asia, South America, and the Canadian Arctic. Because these smaller glaciers are melting quickly, they contribute about the same amount to sea level rise as meltwater from massive ice sheets.

The Water’s Getting Warm

As seawater warms, it takes up more space. When water molecules get warmer, the atoms in those molecules vibrate faster, expanding the volume they take up. This phenomenon is called thermal expansion. It’s an incredibly tiny change in the size of a single water molecule, but added across all the water molecules in all of Earth’s oceans – a single drop contains well over a billion billion molecules – it accounts for about a third of global sea level rise.

So Much to See

While sea level is rising globally, it’s not the same across the planet. Sea levels are rising about an eighth of an inch per year on average worldwide. But some areas may see triple that rate, some may not observe any changes, and some may even experience a drop in sea level. These differences are due to ocean currents, mixing, upwelling of cold water from the deep ocean, winds, movements of heat and freshwater, and Earth’s gravitational pull moving water around. When ice melts from Greenland, for example, the drop in mass decreases the gravitational pull from the ice sheet, causing water to slosh to the shores of South America.

That’s where our view from space comes in. We’re launching Sentinel-6 Michael Freilich, an international partnership satellite, to continue our decades-long record of global sea level rise.

No matter what happens in life, be good to people. 

Being good to people is a wonderful legacy to leave behind.

[ Taylor Swift ]

“There are some people who could hear you speak a thousand words, and still not understand you. And there are others who will understand. without you even speaking a word.”

— Yasmin Mogahed

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