The reading passage claims that scholars are investigating a project sending humans to the mars as well as the moon. But it may create some problems owing to the fact that it is far away than the moon and the project might be impossible at this time. However, the lecturer finds all the ideas dubious and presents some evidence to refute them all.
First, the author embraces the idea that mission to the mars will take two years and supply foods, water, and oxygen is a hard task to do in comparison with the moon mission. In contrast, the lecturer underlines the idea that astronauts can rely on hydroponics. In fact, they can grow some plants in water, which require less space. In this way, not only can they recycle wastewater and drink it but also can use from oxygen released by these plants.
The author also asserts that astronauts on Mars are in the zero-gravity environment of space and it might create some deleterious effects on their bodies, muscle mass, and bone density. On the contrary, the professor brings up the idea that many astronauts spend more time on some space stations and they use several techniques to cope with this situation like regular exercises.
Finally, as set forth by the author space radiations emitted by the sun also might have negative effects on astronauts because there is no magnetic shield to protect astronauts like the shield preserve people on the earth. Conversely, the speaker dismisses this issue due to the fact that these radiations are not dangerous all the time. In fact, they put people's health into danger occasionally. Also, space crafts could be equipped with special instruments. That being so, astronauts can stay in shielded areas in time where the radiations are severe. 
The reading passage claims that scholars are investigating a project sending humans to the  
mars
  as well
 as the moon.  
But
 it may create  
some
 problems owing to the  
fact
 that it is far  
away
 than the moon and the project might be impossible at this  
time
.  
However
, the lecturer finds all the  
ideas
 dubious and presents  
some
 evidence to refute them all. 
First
, the author embraces the  
idea
 that mission to the  
mars
 will take two years and supply foods, water, and oxygen is a  
hard
 task to do  
in comparison
 with the moon mission.  
In contrast
, the lecturer underlines the  
idea
 that  
astronauts
 can rely on hydroponics. In  
fact
, they can grow  
some
 plants in water, which require less  
space
.  
In
 this way, not  
only
 can they recycle wastewater and drink it  
but
  also
 can  
use
 from oxygen released by these plants.
The author  
also
 asserts that  
astronauts
 on Mars are in the zero-gravity environment of  
space
 and it might create  
some
 deleterious effects on their bodies, muscle mass, and bone density.  
On the contrary
, the professor brings up the  
idea
 that  
many
  astronauts
 spend more  
time
 on  
some
  space
  stations and
 they  
use
 several techniques to cope with this situation like regular exercises. 
Finally
, as set forth by the author  
space
 radiations emitted by the sun  
also
 might have  
negative
 effects on  
astronauts
  because
 there is no magnetic shield to protect  
astronauts
 like the shield preserve  
people
 on the earth.  
Conversely
, the speaker dismisses this issue due to the  
fact
 that these radiations are not  
dangerous
 all the  
time
. In  
fact
, they put  
people
's health into  
danger
  occasionally
.  
Also
,  
space
 crafts could  
be equipped
 with special instruments. That being  
so
,  
astronauts
 can stay in shielded areas in  
time where
 the radiations are severe.