140 Siwa is a large and dark main-belt asteroid

Asteroid

Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...

. It has a composition of a P

P-type asteroid

P-type asteroids have low albedo and a featureless reddish electromagnetic spectrum. It has been suggested that they have a composition of organic rich silicates, carbon and anhydrous silicates, possibly with water ice in their interior...

 (or possibly C-type

C-type asteroid

C-type asteroids are carbonaceous asteroids. They are the most common variety, forming around 75% of known asteroids, and an even higher percentage in the outer part of the asteroid belt beyond 2.7 AU, which is dominated by this asteroid type...

) asteroid. It was discovered by J. Palisa

Johann Palisa

Johann Palisa was an Austrian astronomer, born in Opava in Austrian Silesia .He was a prolific discoverer of asteroids, discovering 122 in all, from 136 Austria in 1874 to 1073 Gellivara in 1923...

 on October 13, 1874, and named after Šiwa, the Slavic

Slavic mythology

Slavic mythology is the mythological aspect of the polytheistic religion that was practised by the Slavs before Christianisation.The religion possesses many common traits with other religions descended from the Proto-Indo-European religion....

 goddess of fertility

Fertility

Fertility is the natural capability of producing offsprings. As a measure, "fertility rate" is the number of children born per couple, person or population. Fertility differs from fecundity, which is defined as the potential for reproduction...

. Siwa has a very flat lightcurve, indicating a spherical body.

The Rosetta comet

Comet

A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...

 probe

Space probe

A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to...

 was to visit Siwa on its way to comet 46P/Wirtanen

46P/Wirtanen

46P/Wirtanen is a small short-periodic comet with a current orbital period of 5.4 years. It was the original target for close investigation by the Rosetta spacecraft, planned by the European Space Agency. It belongs to the Jupiter family of comets, all of which have aphelia between 5 and 6 AU. Its...

 in July, 2008. However, the mission was rerouted to comet 67P/Churyumov-Gerasimenko

67P/Churyumov-Gerasimenko

Comet Churyumov–Gerasimenko, officially designated 67P/Churyumov–Gerasimenko, is a comet with a current orbital period of 6.6 years. It is the destination of the European Space Agency's Rosetta spacecraft mission, launched on March 2, 2004....

and the flyby had to be abandoned.