Meteorite climate impact

The iridium in these rocks is supposed to have arrived with a giant meteorite, the impact of which raised debris in such quantity that solar radiation was absorbed for a long time, changing the earth s climate [32.9]. 

Some have left behind them traces of elements rare on Earth, such as iridium. The detection of traces of iridium from a large meteorite has led to a proposal that major extinction of species on Earth, namely the dinosaurs, could be due to the meteorite impact, causing chemical, light and temperature fluctuations, i.e. global climate changes, though this proposal is not universally accepted. 

Compared to the Moon, meteorites have a greater chance to survive impact on Mars because of its atmosphere. Compared to Earth, the current extremely arid climate on Mars lets meteorites... 

Perhaps the best known of the mass extinctions is that associated with the demise of the dinosaurs at the Cretaceous—Tertiary boundary, which has been attributed to a meteorite impact (Alvarez et al. 1980 Kruge et al. 1994 Skelton et al. 2003), although natural climate change may also have been a factor. Planktonic organisms (particularly foraminiferans, calcareous phytoplankton and radiolarians) were also severely affected. On land, trees seem to have been devastated, with the recovery period marked by the proliferation of ferns. The pollen record is dominated by fern spores, and hence known as the fern spike, which is observed... 

Fig. 18.7 The Wilkes Land subgladal meteorite-impact crater was identified on the basis of gravity data obtained by the GRACE sateUite (Gravity Recovery and Climate Experiment). The location of the crater is indicated by a positive free-air gravity anomaly which occurs above a subglacial basin at 70°S and 120°E outlined by the solid white lines which delineate the rim of the crater. The dashed lines outline the hypothetical outer rings of this multi-ring basin. The coincidence of a positive gravity anomaly over a deep...

So Mars may have experienced warm and cold climates episodically in its history. The reasons for climate changes on Mars can be manifold. Besides changes of the obliquity of its spin axis that certainly happened, other effects such as large volcanic eruptions, impacts of large meteorites and others have to be considered (see also Kargel and Strom, 1996 [178].) Climatic change on Mars caused by impact basin formation was studied by Matsui, Tajika, and Abe, 1988 [220]. 

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