Deep below the ground, radioactive elements break up water molecules(分子), producing ingredients that can fuel subsurface life. This process, known as radio-lysis(辐射分解), has sustained bacteria in isolated, water-filled cracks on Earth for millions to billions of years. Now a study published in Astro-biology shows that radiolysis may have supported life in the Martian subsurface.
Dust storms, rays in the universe and solar winds ruin the Red Planet's surface. But below-ground, some life might find refuge. "The environment with the best chance of habitability on Mars is the subsurface," says Jesse Tarnas, a planetary scientist at NASA. Examining the Martin underground could help scientists learn whether life could have survived there. And the best subsurface samples available today are Martin meteorites(陨石)that have crash-landed on Earth.
Tarnas and his colleague evaluated the mineral makeup and radio-active element abundance in the Martin surface using satellite and rover data. They input these data into a computer model that simulated(模拟)radiolysis to see how efficiently the process would have generated hydrogen gas and other chemical ingredients that can sustain the underground bacteria. The researchers report that if water was present, radiolysis in the Martin subsurface could have sustained life for billions of years and perhaps still could today.
Scientists previously studied Mars radiolysis, but this marks the first estimate using Martin rocks to quantify the planet's subsurface habitability. Tarnas and his colleagues also evaluated the potential richness of life in the Martin underground and found that as many as a million bacteria could exist in a kilogram of rock.
The most habitable meteorite samples analysed appeared to be made of a rock type called regolith breccia. "These are thought to come from the southern highlands of Mars, which is the most ancient area on Mars," Tarnas says.
Underground life, as described by this research, would require water and it remains unknown if groundwater exists on the planet, says Lujendra Ojha, a planetary scientist at Rutgers University. Determining whether the Martin subsurface contains water will be an important next step, but this investigation helps to motivate that search. Ojha says, "Where there is groundwater, there could be life."
4. Scientists believe the Martian subsurface might be habitable probably because _________.
A.the Martin surface absorbs rays in the universe |
B.radio-lysis may exist in the Martian underground |
C.radiation combines ingredients for subsurface life to survive |
D.cracks in Martian meteorites overflow with bacteria |
5. What's the purpose of using Martian meteorites?
A.To measure the Martian habitability below-ground |
B.To simulate the process of producing hydrogen. |
C.To help life find shelter from solar winds |
D.To explore the source of hydrogen gas. |
6. What can be inferred from the last 3 paragraphs?
A.Tarnas was the first to study Mars radiolysis. |
B.The Martian underground proved to be rich in bacteria. |
C.The southern highlands of Mars are the most habitable. |
D.The existence of groundwater is key to the investigation findings. |
7. The passage is mainly concerned with _________.
A.the reason for no life on the Martian surface |
B.the source of data for the study of Martian habitability |
C.the possibility of Mars sustaining life through radiation |
D.the richness of radioactive elements below the Martian surface |