Here On Earth: A Natural History Of The Planet
Finding fossils preserved from early Mars might tell us that life once flourished on this planet. We can search for evidence of cells preserved in rocks, or at a much smaller scale: compounds called biosignatures are molecular fossils, specific compounds that give some indication of the organisms that created them. However, over hundreds of millions of years these molecular fossils on Mars are subject to being destroyed or transformed to the point where they may no longer be recognized as biosignatures. Future missions must either find surface regions where erosion from wind-blown sand has recently exposed very ancient material, or alternately samples must be obtained from a shielded region beneath the surface. This latter approach is being taken by the ExoMars rover under development where drilled samples taken from a depth of up to 2 meters will be analyzed.
Here on Earth: A Natural History of the Planet
Carbon dioxide is the primary greenhouse gas contributing to recent climate change. Carbon dioxide enters the atmosphere through burning fossil fuels, solid waste, trees, and other biological materials, and as a result of certain chemical reactions, such as cement manufacturing. Carbon dioxide is absorbed and emitted naturally as part of the carbon cycle, through plant and animal respiration, volcanic eruptions, and ocean-atmosphere exchange.
The carbon cycle is the process by which carbon continually moves from the atmosphere to the earth and then back to the atmosphere. On the earth, carbon is stored in rocks, sediments, the ocean, and in living organisms. Carbon is released back into the atmosphere when plants and animals die, as well as when fires burn, volcanoes erupt, and fossil fuels (such as coal, natural gas, and oil) are combusted. The carbon cycle ensures there is a balanced concentration of carbon in the different reservoirs on the planet. But a change in the amount of carbon in one reservoir affects all the others. Today, people are disturbing the carbon cycle by burning fossil fuels, which release large amounts of carbon dioxide into the atmosphere, and through land use changes that remove plants, which absorb carbon from the atmosphere.
Different greenhouse gases can remain in the atmosphere for different amounts of time, ranging from a few years to thousands of years. In addition, some gases are more effective than others at making the planet warmer. Learn more about Global Warming Potential (GWP), a measure of climate impacts based on how long each greenhouse gas remains in the atmosphere and how strongly it absorbs energy.
Aerosols in the atmosphere can affect climate. Aerosols are microscopic (solid or liquid) particles that are so small that instead of quickly falling to the surface like larger particles, they remain suspended in the air for days to weeks. Human activities, such as burning fossil fuels and biomass, contribute to emissions of these substances, although some aerosols also come from natural sources such as volcanoes and marine plankton.
The world's most popular natural history museum is dedicated to understanding the natural world and our place in it. Delve into the fascinating story of our planet, from its fiery beginnings through billions of years of transformation, and explore life on Earth through exhibitions and activities, collection objects and research that happens in the lab and in the field. The museum is larger than 18 football fields and is home to the largest natural history collection in the world.
The Oklo fission reactors are the only known examples of a natural nuclear reactor here on Earth, but the mechanism by which they occurred lead us to believe that these could occur in many locations, and could occur elsewhere in the Universe as well. When groundwater inundates a uranium-rich mineral deposit, the fission reactions, of U-235 splitting apart, can occur.
Interestingly enough, there are a number of scientific findings we can conclude from looking at the nuclear reactions that occurred here. We can determine the timescales of the on/off cycles by looking at the various xenon deposits. The sizes of the uranium veins and the amount that they've migrated (along with the other materials affected by the reactor) over the past 1.7 billion years can give us a useful, natural analogue for how to store and dispose of nuclear waste. The isotope ratios found at the Oklo sites allow us to test the rate of various nuclear reactions, and determine if they (or the fundamental constants driving them) have changed over time. Based on this evidence, we can determine that the rates of nuclear reactions, and therefore the values of the constants that determine them, were the same 1.7 billion years ago as they are today.
On any world, as long as a rich vein of near-surface uranium ore is produced with greater than 3/97 ratio of U-235 to U-238, mediated by water, it's eminently plausible for a spontaneous and natural nuclear reaction to occur. In one serendipitous location on Earth, in more than a dozen instances, we have overwhelming evidence for a nuclear history. In the game of natural energy, don't ever leave nuclear fission off the list again.
The species that you and all other living human beings on this planet belong to is Homo sapiens. During a time of dramatic climate change 300,000 years ago, Homo sapiens evolved in Africa. Like other early humans that were living at this time, they gathered and hunted food, and evolved behaviors that helped them respond to the challenges of survival in unstable environments.
Aired in early 2021, this series focuses on the natural forces which shape our planet, and enable life to flourish here: the sun, volcanoes, oceans, and weather. In addition, the programme takes a look at how humans have impacted the planet and its environments and wildlife.
Early in 2020, BBC One announced a unique collaboration for a special natural history documentary, titled Planet Earth: A Celebration, which aimed to lift viewers' spirits during the uncertain times of the coronavirus pandemic.
David Attenborough narrates the natural history of the world's oceans in this beautifully-filmed documentary. Billed as "the first-ever comprehensive series on the natural history of the world's oceans" this truly was a groundbreaking series, showing us species and behaviour never before filmed using (at the time) state-of-the-art underwater photography techniques. The score for this series, composed by George Fenton, is particularly beautiful.
Life on Earth features a young Attenborough and set a benchmark for natural history documentaries, firmly placing the broadcaster as a household name. It provides a comprehensive story of life, from the very first primitive cells to the evolution of homo sapiens. This is a must-see, even if it is just to watch the best remembered sequence when Attenborough comes face to face with an adult female gorilla in Rwanda (hint: twelfth episode). 041b061a72