Ves­ta and Ceres: born at the same time and yet so dif­fer­ent

Vesta and Ceres vs Mars
Ves­ta and Ceres vs Mars
Image 1/4, Credit: NASA/JPL/John Hopkins University/Space Telescope Science Institute/MSSS/ESA/DLR.

Vesta and Ceres vs Mars

Ves­ta and Ceres are small bod­ies. The plan­ets of the So­lar Sys­tem were cre­at­ed from such frag­ments a long time ago. Both bod­ies are shown in a size com­par­i­son with Mars.
Up and down on Vesta's crater-strewn surface
Up and down on Ves­ta's crater-strewn sur­face
Image 2/4, Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Up and down on Vesta's crater-strewn surface

NASA's Dawn space­craft ob­tained this im­age with the Fram­ing Cam­era on 11 Au­gust 2011 us­ing the clear fil­ter. The im­age has a res­o­lu­tion of about 260 me­tres per pix­el.
Piece of the Millbillillie eucritic meteorite, thought to come from Vesta
Piece of the Mill­billil­lie eu­crit­ic me­te­orite, thought to come from Ves­ta
Image 3/4, Credit: DLR (CC-BY 3.0).

Piece of the Millbillillie eucritic meteorite, thought to come from Vesta

A piece of the Mill­billil­lie eu­crit­ic me­te­orite, thought to come from Ves­ta, which fell to Earth on 15 Oc­to­ber 1960 in the Wilu­na dis­trict of West­ern Aus­tralia.
Structure of the dwarf planet Ceres
Struc­ture of the dwarf plan­et Ceres
Image 4/4, Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

Structure of the dwarf planet Ceres

Plan­e­tary re­searchers es­ti­mate that Ceres has a con­sid­er­able amount of wa­ter - 15 to 25 per­cent of its mass - which is hid­den be­low the crust in the form of a 100 kilo­me­tre-thick wa­ter-ice man­tle.

Asteroids, also known as minor planets, differ greatly in shape and size. Those with which we are more familiar are in almost all cases crater-strewn irregularly shaped bodies that can even have tiny moons. Most of them have a diameter of between 20 to 100 kilometres, a few up to 500 kilometres, but none are larger than Ceres: with its 1000- kilometre diameter, it makes up more than a third of the total mass of the asteroid belt.

Vesta, with a diameter of between 460 and 580 kilometres, is the third largest asteroid. It rotates around its own axis in five hours and 20 minutes, and requires 3.6 Earth years to complete an orbit around the Sun. As this asteroid is relatively close to the sun at 380 million kilometres, the light elements in the rock have evaporated and escaped into space.

It is assumed that only a very small percentage of water ice has remained, which is why planetary researchers describe Vesta as 'dry'. Spectroscopic observations with Dawn show that Vesta's crust consists of various types of rock. At the south pole, the collision with another asteroid has left a huge impact crater with a diameter of 460 kilometres and a depth of about 13 kilometres. Planetary researchers assume that the impact produced at least 50 smaller asteroids, which now follow their path around the Sun as 'Vestoids'. It is pretty certain that individual fragments have reached Earth. That is indicated by various meteorite finds in the Antarctic.

Data on the asteroid Vesta

Mass:3.0 x 1020 kg
Size:578 x 560 x 458 kilometres
Density:3.9 g/cm3
Rotation period:5.34 hours
Orbital period:3.63 years
Average distance from the Sun:353.3 million kilometres

It was on the night of New Year in Palermo in 1801 – in what was then the southernmost observatory in Europe – that Italian astronomer Giuseppe Piazzi discovered the dwarf planet Ceres. Before this discovery, eighteenth century scholars had wondered about the gap between Mars and Jupiter; after all, according to the empirical Titius-Bode law on the distances between the planetary orbits, there should have been a planet precisely in that location. With a diameter of 1000 kilometres, Ceres was, however, too small to close that gap on its own. So German astronomers continued their search.

Working together as a 'celestial police force' they noted one object after the other. Vesta was discovered in 1807 by the Bremen physicist and astronomer Heinrich Olbers. By the end of the nineteenth century, astronomers could proudly point to 463 recorded asteroids. Instead of a planet on the far side of Mars they had found the Main Asteroid Belt of the Solar System. Today we know almost half a million objects.

Data on the asteroid Ceres

Mass:8.7 x 1020 kilograms
Size:974 x 974 x 910 kilometres
Density:1.98 g/cm3
Rotation period:9.08 hours
Orbital period:4.6 years
Average distance from the Sun:413.9 million kilometres

The discovery of the Main Asteroid Belt

It was on the night of New Year in Palermo in 1801 – in what was then the southernmost observatory in Europe – that Italian astronomer Giuseppe Piazzi discovered the dwarf planet Ceres. Before this discovery, eighteenth century scholars had wondered about the gap between Mars and Jupiter; after all, according to the empirical Titius-Bode law on the distances between the planetary orbits, there should have been a planet precisely in that location. With a diameter of 1000 kilometres, Ceres was, however, too small to close that gap on its own. So German astronomers continued their search.

Working together as a 'celestial police force' they noted one object after the other. Vesta was discovered in 1807 by the Bremen physicist and astronomer Heinrich Olbers. By the end of the nineteenth century, astronomers could proudly point to 463 recorded asteroids. Instead of a planet on the far side of Mars they had found the Main Asteroid Belt of the Solar System. Today we know almost half a million objects.

Contact
  • Elke Heinemann
    Ger­man Aerospace Cen­ter (DLR)

    Com­mu­ni­ca­tions and Me­dia Re­la­tions
    Telephone: +49 2203 601-2867
    Linder Höhe
    51147 Cologne
    Contact
  • Prof.Dr. Ralf Jaumann
    Freie Uni­ver­sität Berlin
    In­sti­tute of Ge­o­log­i­cal Sci­ences
    Plan­e­tary Sci­ences and Re­mote Sens­ing
    Telephone: +49-172-2355864
    Malteserstr. 74-100
    12249 Berlin
    Contact
  • Ulrich Köhler
    Ger­man Aerospace Cen­ter (DLR)
    In­sti­tute of Plan­e­tary Re­search
    Rutherfordstraße 2
    12489 Berlin
    Contact

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