Caption: This image captured by the Dawn spacecraft is an enhanced color view of
Ceres, the largest object in the asteroid belt. Credit: NASA/JPLCaltech/
UCLA/MPS/DLR/IDA

There are millions of pieces of rocky material left over from the formation of our solar
system. These rocky chunks are called asteroids, and they can be found orbiting our Sun.
Most asteroids are found between the orbits of Mars and Jupiter. They orbit the Sun in a
doughnut-shaped region of space called the asteroid belt.
Asteroids come in many different sizes—from tiny rocks to giant boulders. Some can
even be hundreds of miles across! Asteroids are mostly rocky, but some also have metals
inside, such as iron and nickel. Almost all asteroids have irregular shapes. However, very
large asteroids can have a rounder shape.
The asteroid belt is about as wide as the distance between Earth and the Sun. It’s a big
space, so the objects in the asteroid belt aren’t very close together. That means there is
plenty of room for spacecraft to safely pass through the belt. In fact, NASA has already
sent several spacecraft through the asteroid belt!
The total mass of objects in the asteroid belt is only about 4 percent the mass of our
Moon. Half of this mass is from the four largest objects in the belt. These objects are
named Ceres, Vesta, Pallas and Hygiea.
The dwarf planet Ceres is the largest object in the asteroid belt. However, Ceres is still
pretty small. It is only about 587 miles across—only a quarter the diameter of Earth’s
moon. In 2015, NASA’s Dawn mission mapped the surface of Ceres. From Dawn, we
learned that the outermost layer of Ceres—called the crust—is made up of a mixture of
rock and ice.
The Dawn spacecraft also visited the asteroid Vesta. Vesta is the second largest object in
the asteroid belt. It is 329 miles across, and it is the brightest asteroid in the sky. Vesta is
covered with light and dark patches, and lava once flowed on its surface.
The asteroid belt is filled with objects from the dawn of our solar system. Asteroids
represent the building blocks of planets and moons, and studying them helps us learn
about the early solar system.
For more information about asteroids, visit: https://spaceplace.nasa.gov/asteroid

Caption: An artist’s illustration showing a possible inner structure of Mars. Image credit: NASA/JPL-Caltech

Mars is Earth’s neighbor in the solar system. NASA’s robotic explorers have visited our neighbor quite a few times. By orbiting, landing and roving on the Red Planet, we’ve learned so much about Martian canyons, volcanoes, rocks and soil. However, we still don’t know exactly what Mars is like on the inside. This information could give scientists some really important clues about how Mars and the rest of our solar system formed.

This spring, NASA is launching a new mission to study the inside of Mars. It’s called Mars InSight. InSight—short for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport—is a lander. When InSight lands on Mars later this year, it won’t drive around on the surface of Mars like a rover does. Instead, InSight will land, place instruments on the ground nearby and begin collecting information.

Just like a doctor uses instruments to understand what’s going on inside your body, InSight will use three science instruments to figure out what’s going on inside Mars.

One of these instruments is called a seismometer. On Earth, scientists use seismometers to study the vibrations that happen during earthquakes. InSight’s seismometer will measure the vibrations of earthquakes on Mars—known as marsquakes. We know that on Earth, different materials vibrate in different ways. By studying the vibrations from marsquakes, scientists hope to figure out what materials are found inside Mars.

InSight will also carry a heat probe that will take the temperature on Mars. The heat probe will dig almost 16 feet below Mars’ surface. After it burrows into the ground, the heat probe will measure the heat coming from the interior of Mars. These measurements can also help us understand where Mars’ heat comes from in the first place. This information will help scientists figure out how Mars formed and if it’s made from the same stuff as Earth and the Moon.

Scientists know that the very center of Mars, called the core, is made of iron. But what else is in there? InSight has an instrument called the Rotation and Interior Structure Experiment, or RISE, that will hopefully help us to find out.

Although the InSight lander stays in one spot on Mars, Mars wobbles around as it orbits the Sun. RISE will keep track of InSight’s location so that scientists will have a way to measure these wobbles. This information will help determine what materials are in Mars’core and whether the core is liquid or solid.

InSight will collect tons of information about what Mars is like under the surface. One day, these new details from InSight will help us understand more about how planets like Mars—and our home, Earth—came to be.

For more information about earthquakes and marsquakes, visit: 

https://spaceplace.nasa.gov/earthquakes

An artist’s rendering of the twin GRACE-FO spacecraft in orbit around Earth. Credit: NASA

As far as we know, water is essential for every form of life. It’s a simple molecule, and we know a lot about it. Water has two hydrogen atoms and one oxygen atom. It boils at 212° Fahrenheit (100° Celsius) and freezes at 32° Fahrenheit (0° Celsius). The Earth’s surface is more than 70 percent covered in water.

On our planet, we find water at every stage: liquid, solid (ice), and gas (steam and vapor). Our bodies are mostly water. We use it to drink, bathe, clean, grow crops, make energy, and more. With everything it does, measuring where the water on Earth is, and how it moves, is no easy task.

The world’s oceans, lakes, rivers and streams are water. However, there’s also water frozen in the ice caps, glaciers, and icebergs. There’s water held in the tiny spaces between rocks and soils deep underground. With so much water all over the planet—including some of it hidden where we can’t see—NASA scientists have to get creative to study it all. One way that NASA will measure where all that water is and how it moves, is by launching a set of spacecraft this spring called GRACE-FO.

GRACE-FO stands for the “Gravity Recovery and Climate Experiment Follow-on.” “Follow-on” means it’s the second satellite mission like this—a follow-up to the original GRACE mission. GRACE-FO will use two satellites. One satellite will be about 137 miles (220 km) behind the other as they orbit the Earth. As the satellites move, the gravity of the Earth will pull on them.

Gravity isn’t the same everywhere on Earth. Areas with more mass—like big mountains—have a stronger gravitational pull than areas with less mass. When the GRACE-FO satellites fly towards an area with stronger gravitational pull, the first satellite will be pulled a little faster. When the second GRACE-FO satellite reaches the stronger gravity area, it will be pulled faster, and catch up.

Scientists combine this distance between the two satellites with lots of other information to create a map of Earth’s gravity field each month. The changes in that map will tell them how land and water move on our planet. For example, a melting glacier will have less water, and so less mass, as it melts. Less mass means less gravitational pull, so the GRACE-FO satellites will have less distance between them. That data can be used to help scientists figure out if the glacier is melting.

GRACE-FO will also be able to look at how Earth’s overall weather changes from year to year. For example, the satellite can monitor certain regions to help us figure out how severe a drought is. These satellites will help us keep track of one of the most important things to all life on this planet: water.

You can learn more about our planet’s most important molecule here: https://spaceplace.nasa.gov/water