NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA. Catholic University of America, Washington, DC 20064, USA.
NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.
Science. 2015 Apr 10;348(6231):218-21. doi: 10.1126/science.aaa3630. Epub 2015 Mar 5.
We measured maps of atmospheric water (H2O) and its deuterated form (HDO) across the martian globe, showing strong isotopic anomalies and a significant high deuterium/hydrogen (D/H) enrichment indicative of great water loss. The maps sample the evolution of sublimation from the north polar cap, revealing that the released water has a representative D/H value enriched by a factor of about 7 relative to Earth's ocean [Vienna standard mean ocean water (VSMOW)]. Certain basins and orographic depressions show even higher enrichment, whereas high-altitude regions show much lower values (1 to 3 VSMOW). Our atmospheric maps indicate that water ice in the polar reservoirs is enriched in deuterium to at least 8 VSMOW, which would mean that early Mars (4.5 billion years ago) had a global equivalent water layer at least 137 meters deep.
我们测量了火星全球大气水（H2O）及其氘代形式（HDO）的分布图，显示出强烈的同位素异常和显著的高氘/氢（D/H）富集，表明大量的水损失。这些地图样本反映了从北极冰帽升华的演化过程，揭示了释放的水具有代表性的 D/H 值，相对于地球海洋（维也纳标准平均海水（VSMOW））富集了约 7 倍。某些盆地和地形洼地显示出更高的富集，而高海拔地区则显示出低得多的值（1 至 3 VSMOW）。我们的大气地图表明，极地储层中的水冰至少富集了 8 VSMOW 的氘，这意味着早期火星（45 亿年前）曾经有一个全球等效水层，至少有 137 米深。
