By 2035, NASA wants to land humans on Mars. But reaching the red planet, on average a-round 140 million miles away, will be difficult. Colder than Antarctica and with little to no oxygen, Mars is an unfriendly environment. Besides, the longer it takes astronauts to get there and the longer they stay, the more they are at risk.

That's why scientists are looking at ways to reduce trip time. Seattle-based company Ultra Safe Nuclear Technologies (USNC-Tech) has offered a solution: an NTP engine that could get humans from Earth to Mars in just three months. Such an engine takes advantage of nuclear technology. Currently, the shortest possible trip for an unmanned spacecraft is seven months, but a manned mission is expected to take at least nine months. Shorter missions would limit the astronaut's exposure to space radiation, but there is still concern about the radiation sent out from the nuclear reactor in-side the spacecraft. This would be mitigated through the rocket's design.

To protect people on the ground, the NTP spacecraft would not lift of directly from Earth, Jeff Sheehy, a NASA scientist, adds. Instead, a regular chemical rocket would carry it into orbit, and only then would it fire up its nuclear reactor, Once in orbit, it could do little harm, as heat radiation cannot move through a vacuum(真空). lf disaster hit and the rocket's reactor broke up, the pieces would not land on Earth—or any other planet—for thousands of years. By that time, the radioactive substance would have “naturally got to the point where it wasn't dangerous anymore”.

Michael Eades, director of engineering at USNC-Tech, says that nuclear-powered rockets would be more powerful and twice as efficient as the chemical engines used today, meaning they could travel further and faster, while burning less fuel. “Nuclear-powered rockets will be key to opening up the solar system but it could be at least two decades before they are used widely,” he says, adding that numerous demonstrations and tests would need to be carried out before an astronaut is sent to Mars in an NTP rocket.

【小题1】What do we know about Mars according to the text?

A．It is about 140 million meters away.	B．It is burning hot.
C．It is rich in oxygen.	D．It is challenging to reach.

【小题2】What does the underlined word “mitigated” in Paragraph 2 mean?

A．Shortened.

B．Relieved.

C．Achieved.

D．Simplified.

【小题3】What will probably happen after the NTP spacecraft enters its orbit?

A．The heat radiation will be kept from moving.

B．Its radioactive substance will disappear fast.

C．The broken reactor will be left on Mars.

D．It won't give out nuclear radiation in space.

【小题4】What do Michael Eades’ words indicate about the NTP spacecraft?

A．It will be a breakthrough in space exploration.

B．It has been widely used for NASA.

C．It will fly to Mars without astronauts for tests.

D．It carries more fuel than a regular one.