If a reader of this newspaper had only 23 random people inclined and questioned each of them about their lives, it is more likely than not that two of them would find a birthday.
Known in the mathematical world as a birthday problem, statisticians and probability theorists refer to this scenario to explain the surprising plausibility of events that originally seem dubious.
"What looks incredible at first glance may not be the case when you look at the numbers," says NASA columnist Joe McGregor, describing both the idea behind the problem and justifying its credibility in a completely different discovery.
McGregor, NASA colleagues and a team of Earth Scientists believe they have found a huge crater under the ice cover that lies at the root of Greenland. The revelation described in a study published this week in Geophysical Studies marks the second time that this type of crater was found hidden under the ice.
The first such finding came to light in November, when the researchers warned the world about the 31-kilometer sub-structure of the northwest of Greenland called the Hawaii crater. Considering satellite and geophysical data, McGregor noticed the second crater less than 200 km to the southeast, with the proximity that he considered himself to indicate that craters were created in a binary asteroid collapse.
McGregor and his colleagues think otherwise. They suggest that the crater Hiawatha and the second crater, which is 36.5 km wide, have been formed at separate points sometime since the Pleistocene era some 2.6 million years ago, a mismatch between closeness and time that will make their discovery even more – remarkable.
Of the 200 earth craters whose existence has been confirmed by scientists, only two pairs are spatially close despite the formation of many different times. One set is the craters of Clearwater Lake in northern Quebec, one of which physically overlaps with the other, although his birthday is about 180 million years later.
The other pair is located in Ukraine, 108 km and 104 million years.
"If this couple in Greenland is unrelated, it will be a third such pair, which would be unusual in terms of statistics," says McGregor, who works in Maryland. In fact, inspired by the birthday issue, his colleague William F. Botke, who is a Colorado-based planetary scientist, worked out a statistical model that fixes the number of close but unrelated couples craters likely to exist in the world in one or two.
"But," McGregor continued, "it's hardly a strong argument to say," Oh, wow, there's no way for that to happen. These two (in Greenland) must be related. "
Ice may not hide evidence of what happened to the stone beneath it, as previously thought
In his study, McGregor and his team point out several significant differences between their discovery and the Hawaii crater. Although the size and circular shapes of the craters are similar, the second crater seems to be twice as eroded, and the ice over it is significantly less disturbed, which causes the researchers to assume that the crater of Hiawatha is younger.
So far, the researchers' perception of the formation of each crater is inaccurate. Further research is needed to establish their respective ages, which according to McGregor can be achieved by revealing rocks melted during the impacts created by the craters before recrystallization, a process that would restore the geohronology of the mineral.
This task, McGregor said, would be simpler in the Hawaii crater than in the second crater where the ice is twice as thick as two kilometers.
If, at some point in the future, McGregor's discovery is definitely determined by drilling and geophysical research as a crater of impact, it will be the 22nd world record. He suggested naming him after the end of famed gay scientist Stan Patterson, a Scot who emigrated to Canada as a young adult in 1957 shortly after having participated in one of the first scientific expeditions in this part of Greenland.
"The ice may not hide evidence of what happened to the stone beneath it, as we thought before," McGregor said, considering the significance of his discovery and that of the Hawaii crater.
"More of this geological history remains to be found, both in Greenland and in Antarctica."