http://www.cnbeta.com/articles/science/634617.htm研究人員估算,稀有金屬約佔火星總質量的0.8%。計算機模擬顯示,要在火星上留下這麼多稀有金屬,需要在44.3億年前由一顆直徑1200公里的小行星撞擊火星,加上此後一串小規模撞擊。相關論文已發表在美國《地球物理通訊》月刊上。
https://en.wikipedia.org/wiki/North_Polar_Basin_(Mars)
Some scientists have postulated that the basin formed during the impact of a single, large body roughly 2% the mass of Mars, having a diameter of about 1,900 km (1,200 miles).[1][3] However, the basin is not currently recognized as an impact basin by the IAU.