Over the past few decades, significant research work have revealed that there are certain low gravity regions on Earth. As we know the g-value on earth is 9.8 m/s or 1 approximately. But in these regions, the level of gravity is lower than the normal g-value causing major impact on the thriving environment and the surroundings.

It can be quite surprising to know that the Canadians weigh less than their American neighbours. A large part of Canada actually boasts lower gravity than its surrounding places. Researchers have puzzled over this phenomenon over the years and they seemed to get the idea if it was due to the crust present there rebounding slowly after the end of the last ice age or it could be a deeper issue involving convection in the Earth's mantle - or some other combination of the two. Ultra precise measurements taken by a satellite GRACE (Gravity Recovery and Climate Experiment) have revealed that each effect is equally responsible for Canada's low gravity. The work that has been carried out could shed light on how continents form and evolve over time.

GRACE is a joint mission of NASA and the German Aerospace Center and was launched into space in the year of 2002. The two spacecraft do fly 500 kilometres above the Earth, 220 kilometres apart. , The two spacecraft can measure distance differences between them as tiny as a micron using a microwave ranging system.

That has allowed them to measure significant tiny changes in the distribution of mass - and hence gravity - on the Earth. For instance, if the leading spacecraft encounters an area with more gravity, it would be pulled ever-so-slightly closer to Earth than the trailing spacecraft, and that way that distance can be measured perfectly.

A geophysicist Mark Tamisiea, who performed the work at Massachusetts, US, used GRACE to study the low gravity over Canada's Hudson Bay. This low first came into attention of the scientists in the 1960s. It was the time period when the planet's first global gravity fields were mapped.

It was suspected that it was due to an ice sheet known as Laurentide that had blanketed a sizeable part of North America during the last ice age. At various places, the sheet was more than 3 kilometres thick and thus it sort of had depressed the Earth's crust beneath it.

The ice age ended about 20,000 years ago which caused the ice to rapidly melt. But the crust takes time to spring back and it is rebounding today at the rate of about 12 millimetres per year.

What effect can alterations in gravity level cause on life?
Gravitational acceleration has been proved to remain constant throughout the ~4 billion or Ca or 109 years of biological evolution on Earth. To produce today's Earth, Gravity interacts with other major environmental factors; for example, gravity is responsible for giving weight to objects on Earth so gravity is necessary for rain to fall, for water to drain, for heat to dissipate (i.e., convective force), for air and water to Separate, etc. The folks of Canada seem to acquire low weighted bodies due to this reason only. Apart from this, the low gravity or altered gravity levels can seem to effect the life Canadians in many more ways. Though no further research has been carried out yet but the already existing research shows a lot of what needs to be learnt and perceived. In addition to gravity's influence on the environment, it likely is a major contributor to biological changes given the knowledge of the fact that the species evolve from water to land. To counteract gravity, new land species would require to develop new and enhanced systems for fluid flow and regulation, postural stability, structural support, new systems to deal with the altered environmental conditions and locomotion to function and thrive in a 1-G terrestrial environment. The hyper gravity i.e. increased levels of gravity also effect the basic processes of life on earth. In the context of evolution, the ability to evolve under increased gravity seems to be related to size. Single cells and nematodes can withstand 105-G for brief periods, young plants withstand for 10 minutes at 30-40-G without noticeable structural changes, rats appear to survive 15-G for 10 minutes while 20-G is lethal, and humans are capable of tolerating only 4-5-G for 10 minutes which if increased could be harmful and lethal. Gravitational levels, like other physical environmental factors, appear to determine the boundaries for life thus making it an essential factor in surveillance of life.
In the context of microbes, they are less gravity sensitive than larger species given the fact that the effect of gravity relates to size and thus should have less difficulty in transiting between planets and different gravity levels as compared to humans. The spacecraft and shuttles that carry human life to the space are required to maintain suitable gravity levels and maintain humans off Earth while microbes can survive outside the spacecraft with minimal protection i.e. they don't need to be delivered a requisite amount of gravity.

Microbes fit into many ecological niches and first they adapt rapidly to their environment and then they begin to evolve as soon as an environment is hospitable to them. Complex life forms require complex ecosystems and various other factor for survival and evolution, suggesting that major prototypes of Earth's ecology must be included in the studies to see and study the effects and to allow survival and evolution of these complex forms on other planets. Therefore, the ability of Earth-inhabiting life forms to survive beyond Earth can be determined, at least initially, by relating to the size of organisms and their environmental requirements, as discussed before.

About Author / Additional Info:
A budding Biotechnologist from India. Visit http://in.linkedin.com/pub/shivani-sharma/4b/91b/384 for more details.
Researcher ID- J-4200-2012