How would you describe the importance of microbes?
Microbes are the unseen force that really makes the planet work. They are key players in elemental cycles, so the amounts of certain gases in the atmosphere can be strongly controlled by microbes. Higher life wouldn’t be possible without microbes; they form the basis of the food chain and live in our guts. The human body itself is actually only 10% human cells, and 90% microbes; they are essential to the human experience as we know it.
Microbes are also extremely helpful. Many antibiotics are naturally produced by microbes in order to fight off competition competition or predators – we’re essentially using the carefully crafted result of millions of years of evolution to improve human health enormously. And because there are so many different species of microbes out there, these single celled organisms contain the vast majority of the planet’s biological repository. If we think of each gene as a book, then the microbial library is many, many times larger than that of plants and animals. There are stories we can’t even imagine, “stories” that will help human society in unknown ways.
How do microbes survive these extreme types of conditions you’ve mentioned?
There are many different types of adaptations, each one cleverly suited for the particular challenge the microbe is facing. For example, organisms that live in really salty conditions generate a lot of molecules inside the cell that balance the salt differential. Without these protectant molecules, water would flow into the outer, saltier environment, causing the cells to shrivel up. Radiation resistant organisms do things differently. Radiation is bad because it breaks DNA, making it impossible to effectively produce proteins and carry on the business of metabolism and life. But some microbes have generated a rapid repair system to more quickly piece broken DNA back together again.
It’s also important to realize that the term “extreme” is completely subjective. The extremophiles we’re talking about have had just as much evolutionary time as we humans have, and they’d consider our optimal conditions pretty difficult to deal with. If a microbe is well adapted to live at 200 C, then it would find Los Angeles in the fall a frigid wasteland.
How does this help us understand possible life in outer space?
A longstanding question of astrobiology is, What might life elsewhere in the universe look like? Would it be little green men? Probably not; life forms will be configured metabolically and structurally to best handle their particular environments, as dictated by the principles of evolution, so we don’t necessarily know exactly what we’re looking for.
But given that we only have one example of what life looks like – life on Earth – our search for life elsewhere is driven by what we know. We assume that the laws of physics and behavior of the elements operate similarly on other planets, which would lead to biological building blocks and mechanisms we’re familiar with. This could all be wrong – life could be fundamentally different, perhaps not based on carbon, and this would be very exciting – but it is the best investigatory framework we have. So understanding the crazy diversity of life on Earth and the amazing things it can do essentially broadens the search space – it allows us to look for things beyond Earth that we otherwise would have no idea existed.
What exactly is astrovirology?
The study of extremophiles, along with the rise of genetic sequencing, has taught us that life is pervasive – millions of cells in every breath of air, in our gut, in the deep sea, even inside the rocks of the Earth’s crust. But even more plentiful are viruses, those little packets of DNA that can use a host microbe’s molecular machinery to make copies of itself. Whether or not viruses are really life is another question, but they clearly act as a critical component of the biosphere, moving genetic information around, driving evolution, and occasionally killing lots of cells. As many microbes as there are on the planet – trillions? – there are probably at least 10 times more viruses. They’re tiny and hard to look for, but some people have proposed that viruses may be a good target for missions searching for life. And because viruses can’t replicate on their own, seeing viruses would indicate the presence of viable cells as well: the first sign of life beyond Earth could be a virus, the same entity that most people associate with death and destruction.
What have we learned from the Curiosity mission to Mars?
For one thing, Curiosity has contributed enormously to our knowledge of how to build, manage, and operate a successful robotic mission on another planet. The mission’s complexity is stunning, and the logistical details of how to communicate with the rover, how to build a consensus for rover activities, and how to optimize use of the instruments are very challenging issues. I think NASA has a lot to teach the world when it comes to management and organizational structure.
Scientifically, a few things have been particularly intriguing. The pervasive martian soil appears to contain about 2% water, and the water that used to flow around Curiosity’s current home was essentially drinkable fresh water. A new type of igneous rock was discovered that points to a more complex inner life of Mars – the deep movement of magma inside the planet is still a big mystery. The rover is currently on its way to the central mound of Gale Crater, where layered rocks climb upward into the hazy red sky. Those layers record various periods of the planet’s past, and hopefully Curiosity will be able to decipher the clues.
Why is it important to keep exploring?
Exploration is one of the most fundamental human traits, something that is ingrained in our species and has contributed to our success over the millennia. Because of our constant need for new frontiers and new knowledge – even before we decide it’s useful knowledge – we’re able to anticipate future needs and limit our risk from any particular challenge.
Sometimes it’s hard to see exactly how these explorations will improve everyday life, but history has shown that societies are stronger and more economically vibrant when they’re exploring. Pushing boundaries in the physical sense often leads to a wide range of innovative thinking in technology or the arts – it promotes an openness to new ideas that is primed by exploration.
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Jeffrey Marlow is a graduate student in Geological and Planetary Sciences at the California Institute of Technology where he studies exotic microbial metabolisms in an attempt to understand the limits of life on Earth and beyond. He has followed extreme life forms to acidic rivers, ice caves, deserts, the high Andes, and the deep ocean, and has worked on NASA’s Mars Exploration Rovers, Phoenix Mars Lander, and Mars Science Laboratory. Mr. Marlow has also worked for Google’s marketing team, and writes for Wired.