2025年9月7日
All the Water on Planet Earth
Illustration Credit: Jack Cook, Adam Nieman, Woods Hole Oceanographic Institution; Data source: Igor Shiklomanov
Explanation: How much of planet Earth is made of water? Very little, actually. Although oceans of water cover about 70 percent of Earth’s surface, these oceans are shallow compared to the Earth’s radius. The featured illustration shows what would happen if all of the water on or near the surface of the Earth were bunched up into a ball. The radius of this ball would be only about 700 kilometers, less than half the radius of the Earth’s Moon, but slightly larger than Saturn’s moon Rhea which, like many moons in our outer Solar System, is mostly water ice. The next smallest ball depicts all of Earth‘s liquid fresh water, while the tiniest ball shows the volume of all of Earth’s fresh-water lakes and rivers. How any of this water came to be on the Earth and whether any significant amount is trapped far beneath Earth‘s surface remain topics of research.
Tomorrow’s picture: butterfly webb
地球上的所有水资源
Illustration Credit: Jack Cook, Adam Nieman, Woods Hole Oceanographic Institution; Data source: Igor Shiklomanov
说明: 地球上有多少是由水组成的？其实非常少。虽然海洋覆盖了地球表面约70%的面积，但这些海洋与地球的半径相比是相对浅薄的。这幅特色插图展示了如果地球表面或接近表面的所有水都聚集成一个球体会发生什么情况。这个球体的半径仅约700公里，还不到月球半径的一半，但稍大于土星的卫星瑞亚（土卫五），而瑞亚像我们外太阳系的许多卫星一样，主要由水冰构成。下一个较小的球体代表地球上所有的液态淡水，而最小的球体则显示了地球上所有淡水湖泊和河流的体积。这些水是如何来到地球的，以及是否有大量水被困在地球表面之下，仍然是研究的课题。
明日的图片: butterfly webb