Category The Earth, Earth Science, Planet Earth

          Despite being the closest planet to the Sun, often orbiting less than 60 million kilometres away from the star, temperatures on Mercury can drop below —180°C (-290°F). This is because Mercury is too hot and too small to be able to hold on to much gas. With no clouds to stop heat from escaping into space at night, temperatures on Mercury plummet.

          Mercury is the planet in our solar system that sits closest to the sun. The distance between Mercury and the sun ranges from 46 million kilometers to 69.8 million kilometers. The earth sits at a comfy 150 million kilometers. This is one reason why it gets so hot on Mercury during the day.

          The other reason is that Mercury has a very thin and unstable atmosphere. At a size about a third of the earth and with a mass (what we on earth see as ‘weight’) that is 0.05 times as much as the earth, Mercury just doesn’t have the gravity to keep gases trapped around it, creating an atmosphere. Due to the high temperature, solar winds, and the low gravity (about a third of earth’s gravity), gases keep escaping the planet, quite literally just blowing away.

          Atmospheres can trap heat, that’s why it can still be nice and warm at night here on earth. Mercury’s atmosphere is too thin, unstable and close to the sun to make any notable difference in the temperature.

          Space is cold. Space is very cold. So cold in fact, that it can almost reach absolute zero, the point where molecules stop moving (and they always move). In space, the coldest temperature you can get is 2.7 Kelvin, about -270 degrees Celsius.
          Sunlight reflected from other planets and moons, gases that move through space, the very thin atmosphere and the surface of Mercury itself are the main reasons that temperatures on Mercury don’t get lower than about -180 °C at night.

          The images revealed bright deposits on the floors of some craters — a discovery shrouded in mystery without higher-resolution images –are actually clusters of rimless pits surrounded by halos of reflective material.

          “The etched appearance of these landforms is unlike anything we’ve seen before on Mercury or the moon,” said Brett Denevi, a staff scientist at the Johns Hopkins University Applied Physics Laboratory, in a prepared statement. “We are still debating their origin, but they appear to be relatively young and may suggest a more abundant than expected volatile component in Mercury’s crust.”

          In other words, Mercury’s surface might look a lot like the moon. But evidence of recent volcanic history suggests the planet has more going on than scientists thought.

          Planets are born from the countless collisions of rocks and space debris that were part of the early Solar System. The heat from these impacts remains deep within the core of the planet, released through volcanic eruption. Mercury’s cratered appearance shows that there has been no volcanic activity on the planet for billions of years. This makes Mercury a dead planet.

          Mercury is the closest planet to the Sun, and as a result is a dry, barren planet scorched by solar heat. Parts of Mercury’s surface often exceed 450 °C (840 °F) when the planet is closest to the Sun. However, at night, temperatures can drop by over 600 °C (1,100 °F) and some scientists believe that there is actually ice in deep craters that never see the Sun. Radar imaging of the planet has revealed areas of high reflectivity near the planet’s poles. This may be frozen water carried to Mercury by meteorites.

          This orthographic projection view provides a look at Mercury’s North Polar Region. The yellow regions in many of the craters mark locations that show evidence for water ice, as detected by Earth-based radar observations from Arecibo Observatory in Puerto Rico. MESSENGER has collected compelling new evidence that the deposits are indeed water ice, including imaging within the permanently shaded interiors of some of the craters, such as Prokofiev and Fuller. The MESSENGER spacecraft is the first ever to orbit the planet Mercury, and the spacecraft’s seven scientific instruments and radio science investigation are unraveling the history and evolution of the Solar System’s innermost planet. In the mission’s more than four years of orbital operations, messenger has acquired over 250,000 images and extensive other data sets. messenger’s highly successful orbital mission is about to come to an end, as the spacecraft runs out of propellant and the force of solar gravity causes it to impact the surface of Mercury in April 2015.

Earth is the only planet in the Solar System that has a surface split into geological plates. These plates are constantly moving, carried on oceans of rocky mantle no faster than two centimetres each year. 250 million years ago all of the plates on Earth were compressed together in a giant super-continent called Pangaea. Over millions of years this land mass was pulled apart as forces caused the plates to move away from each other.

The earth has not always looked the way it looks today. In other words, the United States one billion years ago was in a totally different location than it is today!! How does this happen? And why does this happen? Let’s take a look. In order for us to some understand of how the earth has changed over time, we first need to understand some of the things that took place, and are still taking place, in the earth.

What about the internal structure of the Earth? Our best clues about the interior come from waves that pass through the Earth’s material. When earthquakes shake and shatter rock within the Earth, they create seismic waves which travel outward from the location of the quake through the body of the Earth. Seismic waves are disturbances inside the Earth that slightly compress rock or cause it to vibrate up and down. The velocity and characteristics of the waves depend on the type of rock or molten material they traverse.

Studies of seismic waves have revealed two important types of layering in the Earth: chemical and physical. Compositional layering refers to layers of different composition. Physical layering refers to layers of different mechanical properties, such as rigid layers verses “plastic” or fluid layers. 

Compositional layering was the first type of layering recognized. Seismic and other data indicate that the Earth contains a central core of nickel-iron metal. The core is surrounded by a layer of dense rock, called the mantle, that extends most of the way from the core to the surface. Near the surface, the densities of the rocks are typically lower. The crust is a thin outer layer of lower density rock about 3 miles thick under the oceans and about 18.5 miles thick under the continents.

Human beings are late arrivals on planet Earth. Humankind’s earliest ancestor —Australopithecus afarensis — appeared over two million years ago. Neanderthals had evolved by 400,000 years ago, and Homo sapiens, modern humans, only existed around 100,000 years ago. Just how short a time this is can be seen when we look at the history of the Earth as a clock, with 12 o’clock midnight being the time that Earth was formed 4.6 billion years ago. Each hour on the clock represents 383 million years.

Millions of years ago, “humans” may have walked on two legs like us, but they were very different from us. They had to hunt and gather food and they had to brave the environment in order to survive. The structure and anatomy of early humans are much different than humans now. Currently, we humans are much lighter than our ancestors. We have large brains with a skull that has high and thin walls. We have thinner jaws and smaller teeth. Our ancestors millions did not have these features, but the features we see now slowly evolved as time passed.

When we think of humans in the past, we need to think of humans that have some of the same general characteristics as us, but they do not look or act like us.

We are still learning about our ancestors, but we guess that the first humans existed between five and seven million years ago: the median time is six million years ago. These humans walked upright on two legs, just like us. Around 90,000 years ago, these humans started making tools to catch fish. Then, around 12,000 years ago, humans began to grow food and change their surroundings in order to survive and eat. As food became more sustainable, and living became easier, humans began to produce more.

As humans developed and grew, their bodies changed. Their brains became bigger, which helped them to develop new tools, including language. They changed the world around them to better survive harsh and changeable weather. Over time, these humans created civilizations and became what we know as humans now.

It may seem like humans have been around for a while, because six million years seems like a long time; in the overall timeline of the Earth, however, six million years is not very long. The Earth itself is 4.5 billion years old. Nonetheless, the six million years humans have been on Earth has allowed them to evolve, build tools, create civilizations, adapt to their environment, and become the humans we are today.

Nobody knows WHAT conditions are needed for life to begin. Some scientists have suggested that living cells may have been brought to Earth by a comet. When the Giotto probe investigated Halley’s Comet in 1986, it found molecules that were similar to living cells. If a comet like this collided with Earth at the right time, then life may have taken hold. Another theory is that powerful lightning bolts flashing through Earth’s early atmosphere may have caused chemical reactions, which created living cells.

One of the first ideas, popularised by biochemist Sidney Fox in the wake of the Miller-Urey experiment, was that amino acids assembled into simple proteins. In modern organisms, proteins perform a huge range of functions, including acting as enzymes that speed up essential chemical reactions. However, this proteins-first hypothesis has largely fallen out of favour.

A much more popular notion is that life began with RNA, a close cousin of DNA, in an “RNA World”. RNA can carry genes and copy itself just like DNA, but it can also fold up and act as an enzyme, just like a protein. The idea was that organisms based solely on RNA arose first, and only later developed DNA and protein.

The RNA World has amassed a lot of supporting evidence, but it is not clear that RNA alone was enough. In recent years, some researchers have suggested that RNA only really reaches its potential when it is paired with proteins – and that both must have existed for life to get started.

A third school of thought is that the first organisms were simple blobs or bubbles. These “protocells” would have resembled modern cells in one key attribute: they acted as containers for all the other components of life. More advanced protocells developed by the Nobel Prize winning biologist Jack Szostak also contain self-replicating RNA.

The final hypothesis is that life began with a series of chemical reactions that extracted energy from the environment and used that energy to build the molecules of life. This “metabolism-first” idea was championed in the late 1980s by Günter Wachtershauser, a German chemist turned patent lawyer. Wachtershauser envisioned a series of chemical reactions taking place on crystals of iron pyrite (“fool’s gold”), a scheme he dubbed the “Iron-Sulphur World”. However, nowadays this idea has been supplanted by Michael Russell’s suggestion that the first life was powered by currents of electrically-charged protons within alkaline vents on the sea bed.

While we cannot know for sure which of these scenarios played out on our planet, successfully creating life from chemicals in the lab would at least tell us which of the proposed mechanisms actually works.