Writing Feedback / Toefl integrated essay：Were there life-form on Mars？ [4]

This is my tofel integrated essay
Theme：summarize the points made in the lecture you just heard，explaining how they cast doubt on points made in the reading。
Thanks a lot ~~~

The reading passage offers three evidences that life-form has existed on Mars 。The lecture completely refutes the passage.
First of all ，the lecture says ，observeing the fossil with the aid of microscopes may change its real characteristic feature ，which make it is similar to the fossils which have been found on earth 。However,this departs from the reading passage,which contends that tube-like fossil can testify that some living things have been there 。

Secondly，the lecture belives that the special chemical compounds found on Mars maybe form by volcanic explosion on earth or come from other non life form activities。Therefore, this directly contradicts what the passage indicates.

Thirdly，oppseing the reading which points grains and bactria have been found on Mars，the lecture demonstrates that the magnetic field on Mars are not as strong the magnetic field on earth，the bacteria are too week to follow the meteorites and the grains were useless.