45亿年前 婴儿期的木星很可能被行星撞击过

45亿年前 婴儿期的木星很可能被行星撞击过

upiter has long been hailed as the mighty “king of planets” thanks to its massive size compared to most of the other planets in our solar system. It’s huge and it’s mostly made of gas, making it difficult for scientists to know what lies deep beneath its thick cloud cover.

与太阳系中的大多数其他行星相比，木星因其巨大的体积一直被誉为强大的“行星之王”。它很大，而且大部分是由气体构成的，这使得科学家很难知道它厚厚的云层下到底有什么。

NASA’s Juno spacecraft has been studying the planet in detail for over eight years now and it’s returned some surprising observations about the planet’s core. Now, a new study from an international team of researchers may offer an explanation.

美国国家航空航天局的朱诺号宇宙飞船，已经对这颗行星进行了8年多的详细研究，并传回了一些令人惊讶的关于该行星核心的观测结果。现在，来自国际研究团队的一项新研究可能会给出一个解释。

Scans from Juno have hinted that Jupiter’s core isn’t exactly what scientists once thought it was. The core isn’t as dense as researchers suspected, but determining why that is has proven to be a challenge.

朱诺号的扫描显示，木星的核心并不是科学家们曾经认为的那样。核心并不像研究人员所怀疑的那么密集，但要确定为什么会这样显然是一个挑战。

“This is puzzling,” Andrea Isella, co-author of a new study published in Nature, said in a statement. “It suggests that something happened that stirred up the core and that’s where the giant impact comes into play.”

发表在《自然》杂志上的一项新研究的合著者安德里亚·伊塞拉在一份声明中说：“这令人费解。”“表明这里曾发生了什么事情，搅动了核心，这就是巨大影响产生的地方。”

To get to the bottom of the mystery, the team ran computer simulations of early Jupiter to see what kind of interactions may have led to the planet’s present state. What they found was that a massive impact, while the planet was still forming, is likely the best explanation.

为了弄清这个谜团的真相，研究小组对早期的木星进行了计算机模拟，看看是什么样的相互作用导致了这颗行星目前的状态。他们发现，当行星还在形成时，一次巨大的撞击可能是最好的解释。

“Because it’s dense and it comes in with a lot of energy, the impactor would be like a bullet that goes through the atmosphere and hits the core head-on,” Isella explains. “Before impact, you have a very dense core, surrounded by atmosphere. The head-on impact spreads things out, diluting the core.”

伊塞拉解释说：“因为它密度大，而且能量也很大，撞击器就像一颗子弹，穿过大气层，迎面击中核心。”在撞击之前，有一个非常致密的核心，被大气包围。迎面撞击会将物质分散开来，稀释核心。”

The planet that may have struck Jupiter would have to have been huge, according to the simulations. The researchers estimate that it would have been roughly 10 times as massive as Earth and it would have messed things up so dramatically that it would take billions of years to settle back down, explaining why the core of Jupiter isn’t nearly as dense and compact as scientists think it should be.

根据模拟，撞击木星的那颗行星可能非常巨大。研究人员估计，它的质量大约是地球的10倍，而且它会把事情搞得如此严重，以至于需要数十亿年才能稳定下来，这就解释了为什么木星的核心不像科学家们认为的那么致密和紧凑。