You are a botanist hired in the future to make a distant planet, Xyloph, habitable for human life. Your job is to help seed the planet with plant life by working with the terraforming team. All four major kinds of plants will be introduced into this new world. You are to help familiarize the terraforming team with the four different kinds of plants on earth. In three well developed paragraphs, describe each of the four major plant groups (seedless vascular, nonvascular, angiosperms, and gymnosperms). Your description should include, but not be limited to, the following: Description of general physical features and characteristics of each plant group. Discussion of living conditions where each plant group survives best. Explanation of specific abiotic conditions necessary for the success of that group, when applicable.

A series of missions to the moons of Jupiter and Saturn has revealed their potential to harbour life. Nina Notman looks to the skies

After a series of mission failures, July 1965 saw the first successful flybys of Mars. The US Mariner 4 became the first spacecraft to take close up pictures of another planet, beaming 22 images of the impact-cratered Martian surface back to Earth. Since then, more than 20 successful missions have explored the red plant’s atmosphere and surface.

Thanks to the images and data collected– and by telescopes, both on earth and in space – we now know that billions of years ago, Mars had the three critical ingredients for life. It had an abundance of the chemical building blocks, liquid water on its surface and an energy source (volcanic activity) to power the chemical reactions that make life possible (on Earth that energy source is the sun). Today, the inhospitable surface of Mars is thought to be unsuitable for life, but the possibility of life existing deep beneath its frozen surface hasn’t been ruled out. To date though, no evidence of life – ancient or otherwise – has been found. Mars being habitable, it turns out, doesn’t mean it actually has a habitat.

Source: NASA/JPL-Caltech/MSSS

Mars has all the ingredients for life – water, chemicals and energy – but no signs of living things yet

The search for Martian life is ongoing, with a further three missions to Mars planned to launch over the next few years. Longer-term, a number of space agencies are also aiming to collect samples from Mars and return them to Earth for more in-depth analysis. And the search for signs of extraterrestrial life is stretching to the depths of our solar system and beyond.

a community that experiences major changes undergoes progress

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.