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The words
Scientists have [discovered / discovery] new things about the atmosphere and environment on Mars. They found a "toxic cocktail" of [chemical / chemicals] that would easily kill [many / any] living organism. The chemicals have [been / being] found on the surface of the Red Planet. The scientists, from Edinburgh University in the UK, say the [discovery / discover] of the chemicals means the chance of finding [alive / life] on Mars has fallen. The scientists are astrobiologists – they study the [atmospheric / atmosphere] and environments in the universe that might [support / supporting] life. The researchers said Mars had no ozone layer, which means there are [height / high] levels of ultra-violet (UV) radiation. The mix [of / off] UV radiation and the chemicals sterilized the Martian landscape.

The scientists tested what [happening / happens] when the chemicals found on Mars mix with UV radiation. They found it killed [organs / organisms] very quickly. The chemicals [alone / lonely] were enough to kill living organisms. However, when the chemicals were [mixture / mixed] with UV rays, the mix killed organisms 11 times [faster / fastest] . The scientists said: "Our observations show that the surface of present-day Mars is highly harmful to cells, [cause / caused] by a toxic cocktail of chemicals and UV radiation." They added that their research was [farther / further] evidence that the surface of Mars is deadly to any [form / from] of plant life. They say the chemicals and UV rays [do / make] "much of the surface and near-surface [regional / regions] uninhabitable".

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