Extraterrestrial bodies

Except for the moon and the planet Mars, no extraterrestrial body has had pieces of its mass directly examined by scientists in an earthly laboratory. This means that there has been no laboratory sample preparation scheme performed on samples of solid matter from any of the other planets, their moons, comets, or asteroids. And yet we read repeatedly about how scientists have been able to surmise the... 

An interesting story as to how most of the iridium appeared on Earth was explained recently by scientists who discovered a thin layer of iridium in the sediments that were laid down in the Earth s crust at the end of the Cretaceous period. This was a period about 65 million years ago when meteors and asteroids crashed into the Earth. These extraterrestrial bodies contained a high percentage of iridium. Dust from the impact spread around the Earth and blocked the sun for months, resulting in the extinction of many plants and animals, including the dinosaurs. This extensive dust cloud also deposited a thin coat of the element iridium that was contained in the fiery bolides. 

The Apollo lunar samples have provided the first opportunity for the analysis of material collected from an extraterrestrial body under carefully controlled conditions. No definitive evidence about the concentration and nature of lunar carbon was provided by the a back-scattering experiments carried out by the Sureveyor unmanned landers. However, these remarkably successful experiments did indicate a magmatic origin for the samples analysed1"3. This was confirmed by the Apollo missions, three distinct samples types being collected from the lunar regolith ... 

Comets and meteorites are examples of astronomical bodies whose behavior can be predicted with a high degree of reliability (comets) or with only the lowest reliability (meteorites). This chapter deals with both types of astronomical bodies, as well as other bodies about which scientists are just beginning to obtain detailed information—asteroids—and the only extraterrestrial body on which humans have set foot—the Moon. 

The efficiency of this method was again demonstrated by Bekov et al. (1988) when detecting Rh traces in natural samples. Extraordinarily high concentrations of iridium and other siderophiles were discovered in the Cretaceous/Tertiary (K/T) boundary deposits and interpreted (Alvarez et al. 1980) as a result of a large extraterrestrial body falling upon the Earth, causing mass extinction of the biota dominant in the... 

If the production of aerosol by fires is large enough to cause reductions in the penetration of sunlight to ground level by a factor of a hundred, which would be quite possible in the event of an all-out nuclear war, most of the phytoplankton and herbivorous zooplankton in more than half of the Northern Hemisphere oceans would die [42]. This effect is due to the fast consumption rate of phytoplankton by zooplankton in the oceans. The effects of a darkening of such a magnimde have been discussed recently in connection with the probable occurrence of such an event as a result of the impact of a large extraterrestrial body with the earth [43]. This event is believed by many to have caused the widespread and massive extinctions which took place at the Cretacious-Tertiary boundary about 65 million years ago. 

---