英语翻译NASA’s methodical approach to the exploration of Mars ha

英语翻译
NASA’s methodical approach to the exploration of Mars has not yet answered the questions of whether biological life forms ever emerged on Mars and whether,[presuming such life forms left fossil traces to begin with],those traces still exist in some moist recesses of the cold and arid planet.
主要是begin with的意思不太明白?难道是“假设这种生命形态留下了化石线索以供人们探索”?