For the first time, two rovers from Earth have reportedly landed on an asteroid not from Earth. The Japanese Space Agency JAXA says it recently made history by putting the unmanned exploration robots on the asteroid's surface. First, the mission, it's cost is estimated at $150 million. It launched in December of 2014 and finally got near the asteroid this summer and it's Japan's second mission of this kind.
The last one to a different asteroid was able to bring some samples back to Earth but it had some technical failures with it's rover. The asteroid itself is more than 100 million miles away from Earth and Japan's goals this time around included getting detailed information about the rock's surface, using explosives to gather material from just beneath that surface and then bringing samples back to Earth by the end of 2020. A total of three rovers will be used to do all this. The vehicles themselves aren't particularly big. The spacecraft that got them there is about the size of a large refrigerator. So the rovers it carried are smaller than that.
These vehicles don't drive over the rock surface like an interplanetary dune buggy. Rather they hop jumping almost as high as 50 feet at a time.
The asteroid they're on is just over a half a mile wide. Scientists think it's rich in water and organic materials and that the samples they get from it will help advance their knowledge of solar system's start-up. If everything goes according to plan, JAXA says this will be the first sample return mission to this type of asteroid. NASA has a similar mission in it's planning but that one isn't due back to Earth until the year 2023.
上次任务在另一颗小行星登陆，并成功地将一些样本带回地球，但是上次投放的漫游车发生了技术故障 。这次登陆的小行星与地球的距离超过1亿英里，日本这次任务的目标包括采集小行星表面的详细信息，利用爆破采集地球以下的物质，并在2020年底前将样本带回地球 。这些任务将由三辆漫游车共同完成 。这些漫游车本身不是特别大 。投放漫游车的航天器的大小相当于一个大型冰箱 。而其搭载的漫游车则较小一些 。
这些漫游车不会像星际沙地车一样在岩石表面行驶 。而是在小行星表面跳跃前行，每次的跳跃高度可达50英尺 。
此次登陆的小行星宽度只有0.5英里多一点 。科学家认为，这颗小行星富含水和有机材料，从这颗小行星上采集的样本将有助于拓展他们对太阳系起源的了解 。日本宇宙航空研究开发机构表示，如果一切按计划进行，这将是此类小行星首个取样返回任务 。美国航空航天局（NASA）计划开展类似任务，不过该任务到2023年才能将样本送回地球 。
1. be able to do sth. 可以…的，能够…的；
He was both willing and able to subordinate all else to this aim.
2. a total of 总数；总额；合计；
The companies have a total of 1,776 employees.
3. be rich in 富含…的；含有大量…的；
Fruits, vegetables, and wholegrains are rich in potassium.
4. according to 按照计划；如同料想的那样；
What you're likely to experience on day two is that things don't go quite according to plan.