While their sizes have yet to be determined precisely, these three structures are clearly very old, and in the case of Woodleigh and Tookoonooka they have become buried beneath a mantle of younger sediments, such that they are no longer visible at the surface.
The sculptured landscapes of hills and valleys are occasionally pitted by regular circular structures, often mere hints.
At other times they are clearly recognisable as large, deep craters.
SEE GALLERY: Meteorite craters in Australia In Australia seven distinct craters, ranging in size from about 25m to around 1km in diameter, have been recognised. In addition, there are another 30 very much larger but deeply eroded and enigmatic circular scars that present some evidence of an origin by impact.
Among the largest are Woodleigh in Western Australia (60-70km across), Lake Acraman in South Australia (greater than 35km) and Tookoonooka in Queensland (50km in diameter).
On land, 11 structures tentatively identified as possible impact sites include: At this stage the origin of these structures, both on land and in the sea, are considered speculative.
In total, some 50 of them have been recognised in Australia, to highly varying degrees of certainty. But was the source of the explosions from within Earth's crust, or was it an extraterrestrial source, such as a giant meteorite, asteroid or comet hitting Earth?
Scientists must often act as sleuths to investigate the evidence of impacts.
Some of the rocks in the Pilbara region of Western Australia, for instance, are 3.5 billion years old, while other sedimentary rocks from Mt Narryer, WA, have been dated at around 3 billion years and contain much older mineral grains derived from pre-existing rocks that are 4.4 billion years old.
Some of these ancient rocks have lain undisturbed for almost a billion years.
The Australian landscape has been gradually transformed by weathering, which still continues at a gentle pace.
But a few features scattered over the land seem to defy any explanation by way of Earth's typically slow weathering and geological processes.