243 Ida

Ida is a big rock in space.

It flies between Mars and Jupiter. This rock is shaped like two big pieces joined together.

It has a tiny moon named Dactyl. The moon stays close to Ida. The surface of the rock is covered in many holes. These holes come from space rocks hitting it. The rock also has a layer of dust and small bits. This dust makes some parts look red. It is a very bumpy place to visit!

243 Ida is a large asteroid in space.

It lives in the asteroid belt between Mars and Jupiter. An astronomer named Johann Palisa found it in 1884. Ida is shaped like two big pieces joined together. It has a very bumpy surface. This surface is covered in many holes called craters. These craters are made when space rocks hit it.

Ida is also covered in regolith. Regolith is a thick layer of loose rock and dust. Space weathering can change how it looks. This is a way that space changes the surface over time. It makes older parts of the asteroid look more red.

Ida was the first asteroid found to have a moon. Its moon is named Dactyl. Dactyl is much smaller than Ida. The two share many of the same traits. This suggests they may have started from the same place. Scientists learned a lot about Ida from the Galileo spacecraft.

This mission helped us understand how asteroids are made.

243 Ida is a very special asteroid in space.

It lives in the asteroid belt between Mars and Jupiter. This asteroid is part of a group called the Koronis family. Scientists think these asteroids are pieces of a much larger object that broke apart long ago. Ida is an S-type asteroid. This means it is made of certain types of rocky minerals. These asteroids are the most common kind in the inner part of the belt.

Ida has a very strange and bumpy shape. It is long and thin, almost like two big rocks joined together. There is a narrow part in the middle called a "waist." This shape makes its gravity very uneven. Because the gravity is so weak, an astronaut could jump from one side to the other. The surface is also covered in regolith. Regolith is a thick layer of loose dust and crushed rock.

This dust is made when space rocks hit the surface. Over time, a thing called space weathering happens. This process makes older parts of the surface look more red.

People have been studying Ida for a long time. An astronomer named Johann Palisa discovered it on 29 September 1884. He worked at the Vienna Observatory in Austria. A man named Moriz von Kuffner gave the asteroid its name. He named it after a nymph from Greek mythology. Later, a scientist named Kiyotsugu Hirayama found that Ida belongs to the Koronis family in 1918. This helped us understand how asteroid groups form.

In 1993, a spacecraft named Galileo visited Ida.

Galileo was launched by the Space Shuttle Atlantis in 1989. The spacecraft flew past Ida on 28 August 1993. During this trip, it took many amazing pictures. These images showed that Ida is covered in many craters. The largest crater is called Lascaux. Some craters are very old, while others like Azzurra look fresh. The mission also helped us link asteroids to meteorites that fall to Earth. We now know many S-type asteroids are the source of ordinary chondrite meteorites.

One of the biggest surprises was finding a moon.

A mission member named Ann Harch found the moon in the Galileo images. The moon is named Dactyl. It is much smaller than Ida, about 1/20th the size. Dactyl and Ida look very similar. This suggests they likely formed from the same original material. Learning about Ida and its moon helps us understand how the whole Solar System works. It shows us how small rocks and moons stay together in the dark of space.

243 Ida is a significant asteroid located in the main asteroid belt. This belt lies in the vast space between the planets Mars and Jupiter.

Ida belongs to a specific group known as the Koronis family. Astronomer Kiyotsugu Hirayama proposed in 1918 that this family consists of fragments from a single, destroyed precursor body. Scientists classify Ida as an S-type asteroid. This means it is composed of stony materials. S-type asteroids are the most common type found in the inner part of the asteroid belt. Studying Ida helps scientists understand the history of our Solar System.

Ida has a very unusual and irregular physical shape. It is elongated, meaning it is stretched out rather than round. In fact, Ida is 2.35 times as long as it is wide. The asteroid appears to be made of two large, solid components connected together. These two halves are separated by a narrow section called a "waist." This shape creates a very uneven gravitational field across the surface. Because the mass is concentrated in the two main halves, gravity is weakest near the waist. The gravitational acceleration on the surface ranges from 0.3 to 1.1 cm/s². This pull is so weak that an astronaut could leap from one end of the asteroid to the other.

The surface of Ida is shaped by constant impacts from space debris. It is one of the most heavily cratered bodies explored in the Solar System. These impacts have reached a saturation point. This means new craters often erase the evidence of older ones. The craters vary greatly in size, age, and appearance. Some are simple, bowl-shaped holes with no central peaks. Others, like the asymmetric crater Fingal, show sharp boundaries between their walls and floors.

The largest crater on Ida is named Lascaux. Most of the largest craters are found in one half of the asteroid, known as region 2.

Ida is covered by a thick layer of loose material called regolith. This regolith is a blanket of pulverized rock and dust about several meters thick. It is created when space rocks strike the surface and break the solid rock into tiny pieces. The regolith is made of silicate minerals, specifically olivine and pyroxene. Large fragments of rock, called ejecta blocks, are also embedded in this dust.

Scientists have observed space weathering on the surface. This is a process where the surface changes over time due to exposure to the space environment. Space weathering causes older regolith to appear more red in color. Freshly exposed material looks different and more like the minerals found in certain meteorites.

One of the most important discoveries during the Galileo mission was Ida's moon.

A mission member named Ann Harch discovered the moon, Dactyl, in images sent back by the spacecraft. Dactyl is much smaller than Ida, measuring about 1/20 the size of the asteroid. Dactyl and Ida share many similar characteristics. This similarity suggests that they have a common origin and formed from the same material. While the exact orbit of Dactyl is difficult to determine, its stability helps scientists estimate Ida's density. Data shows that Ida's density is less than 3.2 g/cm³. This low density proves that Ida is not made of heavy, metallic minerals like iron and nickel.

The history of Ida's discovery began on 29 September 1884. The Austrian astronomer Johann Palisa discovered it at the Vienna Observatory. This was the 45th asteroid he had found. Moriz von Kuffner, a brewer and amateur astronomer, gave the asteroid its name. He chose Ida after a nymph from Greek mythology who raised the god Zeus. In 1993, the uncrewed Galileo spacecraft visited Ida while traveling to Jupiter.

The spacecraft flew by Ida on 28 August 1993 at a speed of 12.4 km/s. This flyby provided the first detailed look at the geology of an S-type asteroid.

This mission changed how scientists view the relationship between asteroids and meteorites. Before the flyby, the exact makeup of S-type asteroids was a mystery. Scientists debated if they were made of stony-iron or ordinary chondrite materials. The data from Ida showed that freshly exposed parts of the surface match ordinary chondrite meteorites. These are the most common meteorites found on Earth. By studying Ida, scientists can now connect the rocks that fall to our planet to specific locations in the asteroid belt. This connection helps us understand where the building blocks of our Solar System came from.