Science by Email 2 December 2011

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	2 December 2011
Rocks from Western Australia's Pilbara region were used to determine oxygen's new birthday. News: Ancient oxygen's new birthday By Patrick Mahony Oxygen gas is a major component of Earth’s atmosphere and is essential for complex life on this planet. Earth is approximately 4.5 billion years old, but it hasn’t always had the oxygen-laden atmosphere that it has today. Previous studies indicated the atmosphere's oxygen gas developed around 2.7 billion years ago. New research linking geology, chemistry and biology suggests oxygen only started to appear in our atmosphere more than 200 million years later. How did scientists come to this conclusion? Using ancient rocks from Western Australia’s Pilbara region, researchers searched for an element called chromium. The ancient Earth had many volcanoes which produced rocks containing chromium. The actions of some ancient microbes generated acid which dissolved the rocks and washed the chromium into the ocean. Scientists can tell the difference between clues left by chromium from rocks and chromium in the ocean. There was little or no chromium in the oceans to begin with, so when the geological record started showing traces of oceanic chromium they inferred that these microbes had evolved. What does this have to do with oxygen? The key is aerobic respiration. Aerobic respiration is a process where organisms use oxygen in air to kick start the chemical reactions needed to get energy. Without oxygen, aerobic respiration can’t occur. The microbes that produced acid which in turn dissolved the chromium were organisms respiring aerobically. Chromium in the oceans instead of rocks indicates the existence of life respiring aerobically which indicates oxygen in the atmosphere. Similarly, the earlier lack of oceanic chromium indicates a lack of oxygen in the atmosphere. The rocks that showed the transition between the types of chromium were 2.48 billion years old, which is where the scientists derived their new date for the development of oxygen in Earth’s atmosphere. More information New evidence for first production of oxygen on Earth Bitesize aerobic and anaerobic respiration Careers Work experience with Geoscience Australia
You will need these materials.   Wash the chopping board, knife and peeler in warm soapy water and dry with a clean tea towel.   Wash your hands with soap and water and dry them with another clean tea towel. Rub a small amount of hand sanitiser into your hands.   Cut the apple into quarters.   Peel one quarter of the apple and seal in a zip-lock bag labelled 'Washed'. Have a friend who hasn't washed their hands for a few hours peel a quarter of the apple and place in another bag labelled 'Unwashed'. Place both bags in a warm place and observe once a day for 1 to 2 weeks. Try this: How clean are your hands?   Safety: This activity involves a knife and mould. See the CSIRO Education safety page for more information. You will need An apple Chopping board Small knife Vegetable peeler 2 zip-lock bags Water Soap Hand sanitiser Dishwashing liquid 2 clean tea towels A friend Marker What to do Wash the chopping board, knife and peeler in warm soapy water. Dry them with a clean tea towel. Wash your hands with soap and water. Dry your hands with another clean tea towel. Rub a small amount of hand sanitiser into your hands, making sure you completely cover your hands. Allow them to dry. Cut the apple into quarters. Peel one quarter of the apple and place it in a zip-lock bag. Seal the bag and label it ‘Washed’. Find a friend who hasn’t washed their hands for a few hours. Have them peel a quarter of the apple and place it in a bag. Label this bag ‘Unwashed’. Place both bags in a warm place away from food for 1 to 2 weeks. Do not open the bags once they have been sealed. Observe the bags each day and compare the two apples. Disposal: throw the bags and their contents into the bin. Do not open the bags. What's happening? Even though your hands might look clean, they can still carry microbes such as bacteria and mould. When you and your friend the peel the apple quarters you transfer some of these microbes to the apple. The microbes feed on the apple, breaking it down and causing it to decay. Cleaning your hands with soap washes away some of the microbes on them. Washing with hand sanitiser kills even more of the microbes. Your friend with the unwashed hands has more microbes on their hands so more are transferred to the apple. This is why their apple decays faster. The process where microbes are passed from a dirty surface to a clean one is known as ‘cross-contamination’. Applications Cross-contamination is a significant hazard in the food industry. Some microbes can make us sick if we eat them, and they can contaminate food if hands and equipment are not cleaned properly. Certain foods, including chicken, eggs and dairy products are particularly susceptible to becoming contaminated. It is important to wash your hands before, during and after food preparation. Cross-contamination can also occur in hospitals. It is important for doctors and nurses to wash their hands and use sterile equipment when treating patients. This is to prevent spreading potentially life-threatening infections and diseases. Try another fruity Science by Email activity More information Food Standards Australia New Zealand: Hand washing tips Food Safety Information Council: Hand washing By Patrick Mahony View online version Quiz questions 1. What can be classified as sedimentary, igneous or metamorphic? 2. What is the chemical product when hydrogen gas combusts with oxygen gas? 3. What do frugivores like to eat? 4. True or false: researchers were able to turn nickel, a heavy metal, into a material 100 times lighter than Styrofoam. 5. What has more impact on the growth of bananas: the temperature they’re grown at, or the length of the day? Did you know? Geoscience Australia has produced the first comprehensive national map of land cover. It is hoped that this resource will be useful to monitor changes in vegetation over time, as well as see the effects of bushfires, floods and drought. Website Hear it! Some particles in space create this familiar sound – what do you think it sounds like? Watch it! Check out this video of a ‘brinicle’ as it reaches its icy finger towards the sea floor. Science at night, Saturday 26 November at 9.00 am on Network Ten Take a deep, oxygen-filled breath – it’s time to get to know the eighth element of the periodic table! This week, we turn up the heat with a little welding, stay a night at an altitude hotel and introduce ourselves to liquid oxygen. So join Dr Rob for an episode brought to you by a big fat capital ‘O’, and watch as the ordinary becomes extraordinary, under the SCOPE. Next episodes: Thursday 8 December: Antarctica Saturday 10 December: Caves Want to have your own episodes of SCOPE to watch whenever you feel like it? Click here to download them directly into your iTunes folder, or go here to download iTunes. Charges apply. Quiz answers 1. Rocks can be classified as sedimentary, igneous or metamorphic. 2. Water (H2O) is the chemical product from the combustion of hydrogen and oxygen. 3. Frugivores like to eat fruit. 4. True. They achieved this by forming the metal into tiny, narrow tubes and arranging it in a lattice. 5. The length of the day has more impact on the growth of bananas than temperature. Research conducted by the University of Western Australia disproved the previous theory that temperature was the main factor in determining banana growth. Science by Email is a CSIRO publication. The Department of Agriculture, Fisheries and Forestry and bankmecu are proud partners of Science By Email. Editor: Jasmine Leong | Manage your subscription | FAQ

 

 

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