Answered Questions

Earth has ideal conditions for the origin of life, i.e. liquid water, organic molecules raining down from space, a protective atmosphere etc. Also these conditions have existed for billions of years. Yet my understanding is life originated only one time on the planet and all life has evolved from that. Why isn't life re-originating from organic compounds on Earth all the time?, Why is there only one evolutionary 'tree of life' on Earth, shouldn't there be many evolving in parallel and new ones sprouting up constantly?

The conditions on Earth when life began were very different from those we have today. As far as we understand, life needed a reducing rather than oxidizing atmosphere, as well as plentiful organic materials. Today the oxygen in our atmosphere and dissolved in the ocean would be a poison for the chemistry that probably...

October 10, 2008 More

Has there ever been a time when the celestial equator was aligned with the galactic plane?

No, at least not for a very long time. I don't know why you are asking. Such "alignments" have no physical or biological significance, and are not of interest or concern to either astronomers or astrobiologists.

David Morrison
NAI Senior Scientist

Is there any evidence of amino acids or other organic compounds being possibly able to "seed" life on other planets?

Organic compounds like amino acids are the chemical building blocks of life, not the seeds of life. We know of a variety of chemical processes that can form such complex organic compounds, and these can indeed be exchanged between planets, by comet impact for example. Many astrobiologists think that some of these building blocks...

October 8, 2008 More

How do we determine the approximate age of the Earth? To me, it seems that due to plate tectonics, eventually all of the land mass on the planet would eventually be recycled into new land. Does this make a difference in the dating process of the earth, since the materials are melted down into the earth's mantle, and then pushed back up again through volcanic activity?

There are ways to date the whole earth using the radioactive decay of uranium into lead, yielding an age of 4.54 billion years, with an uncertainty of about 1%. The most precise dating techniques can be applied only to individual rocks, or mineral grains, or zircon crystals that have not been melted since their...

October 7, 2008 More

Is there any significance to Mars and Earth having almost the same day length and is there any relationship between day length and the ability of a planet to support life?

The rotation periods of planets have been influenced by stochastic or random processes in the early solar system, such as just how large and at what angle the final accretion impacts took place. Mars indeed has a period similar to that of Earth, but Venus, which is our nearest neighbor, has a very different...

October 6, 2008 More

What are the chances of intelligent life living within this universe.... considering that there are billions of galaxies, harboring billions of stars each, most of which have a good chance of having few which are in the habitable zone, why is it that people are so closed mined to the fact that life could exist else where in this universe? If life has evolved on earth, is it too much to believe that other places harbor life?

I agree with your position, and I don't know of any scientist who thinks that we are the only inhabited planet. What surprises me about your question is your statement that people are "closed mined to the fact that life could exist else where in this universe." I have never met anyone who holds...

October 3, 2008 More

The question i have today is why is Nasa always spending money on Mars?? like i mean why bother, there is nothing there for human life. Why dont we forget the past and forget what happened on mars millions of years and look toward the future, maybe trying to locate a planet that already has an atmosphere and upgrade hubble or make a bigger and better hubble to track more planets. What is Nasa trying to accomplish in studying mars??

There are many reasons to study Mars, but for astrobiologists the primary attraction is that Mars is the most likely of the planets in our solar system to support life. In particular, we know that Mars had a warmer climate in the past with liquid water on the surface. All the discoveries from recent...

October 2, 2008 More

Io resembles Earth more than any other world in solar system does. Yet it receives zero attention in NASA. When Galileo was passing by Io on its way to Jupiter its cameras were turned off. Why NASA is searching for signs of life on Mars, where conditions are unfavorable to support life, while Earth-like Io does not receive even a close look?

From some perspectives Io may be Earth-like (actually its size and composition or more similar to the Moon), but not to an astrobiologist. NASA has given a great deal of attention to this moon of Jupiter, and it was one of the prime targets of the Galileo mission that orbited Jupiter during the mid-1990s....

October 1, 2008 More

I read all of your answers on how likely natural catastrophes caused by events in space are, and it all seems quiet safe for now. But are two issues here that make me nervous: a. there is a conflict of interest here: if there was cause of major concern, NASA might have reasons to hide the truth. b. I deal with randomness in my line of work, and every minute I realise how much more significant it is than we all think. Does randomness affect your conclusions? Can "black swans" exist in your predictions?

To answer your question, we must distinguish between things we know and things we don't know. For example, we know that Nibiru (a planet or brown dwarf that will pass between Earth and Sun in four years) does not exist, because if it did, it would have been discovered and tracked by astronomers for...

September 30, 2008 More

Where does water come from exactly? I've found that it's believed that water probably came from meteorite collisions with Earth and the such. Though if it came from other objects... does anyone know how it exactly got there? I'm just confused on how SO much got here.

Water (H2O) is one of the most abundant chemical compounds in the universe. It us made up of hydrogen (the most common element) and oxygen (the third most common element). Anywhere the temperature drops below the condensation point of water, this compound is expected to exist in great abundance. Water is one of the...

September 29, 2008 More