Capitulo 1: El Origen de la Vida. • En una clase de la Historia de la Vida
comenzamos discutiendo su origen. • Sabemos que existe vida en nuestro
planeta.
Capitulo 1: El Origen de la Vida • En una clase de la Historia de la Vida comenzamos discutiendo su origen. • Sabemos que existe vida en nuestro planeta pero no sabemos donde y como se origino. • No tenemos evidencia de vida en ninguna otra parte de nuestro universo. • Debemos suponer que la vida, como la conocemos, se origino en este planeta.
1: El orgánicas Origen complejas de la Vida • Capitulo Existen moléculas en el espacio, cometas, meteoritos etc.. • Estas son el resultado de gas interestelar expuesto a radiación cósmica y estelar. • Estas probablemente se estrellaban contra el planeta Tierra en ocasiones, siendo así una fuente de moléculas orgánicas. • Sin embargo este proceso no resultara en el desarrollo de la vida. Además en nuestro planeta también se pueden formar moléculas orgánicas.
• Para determinar como comenzó la vida en nuestro planeta podemos reconstruir como se formo nuestro sistema solar y nuestro planeta. • Con la ayuda de los biólogos podemos entonces tratar de reconstruir el origen de la vida. • La vida como la conocemos esta compuesta mayormente por agua en su estado liquido. • No podemos imaginarnos que exista vida sin agua, por lo cual necesitamos planetas con agua (océanos) para crear vida.
Origen de Nuestro Sistema Solar • Los astrónomos creen que el universo tiene 15 billones de años de antigüedad. Los primeros elementos comenzaron a formarse (hidrógeno y helio). • Fuerzas gravitacionales colapsaron nubes de estas partículas para formar estrellas. • El 99% de las partículas se unieron para formar estrellas (el sol). • Un 1% de este polvo estelar quedo en orbita alrededor del sol.
Los planetas • Partículas de polvo tienden a unirse por fuerzas electroestáticas en un proceso conocido como “acreción”: – Ej. Mota de polvo debajo de sus camas.
• Planetas pequeños se pueden haber formado de la misma manera cuando las partículas de polvo, en orbita alrededor del sol, se unieron.
Nuestro sistema solar esta compuesto por: Mercurio Venus Tierra Marte Júpiter Saturno Urano Neptuno Plutón De estos solo los primeros 4 Planetas tienen la posibilidad de tener agua en su estado Liquido.
• Cada uno de estos cuatro planetas comenzó como una masa de material derretido como resultado de los choques entre planetas mas péguenos que los formaron. • Eventualmente su capa exterior se enfrío y formo una corteza. • Una ves se enfrío la superficie de los planeta, la temperatura exterior del planeta depende por completo de la distancia del sol y de los gases volcánicos que salen a la superficie durante las erupciones.
Tamaño y distancia del Sol. • A mayor distancia del Sol menos efectos de los rayos solares (mas frió). • El tamaño determina si hay actividad volcánica. Esta actividad volcánica resulta en gases atmosféricos que producen una atmósfera y el efecto de casa de invernadero. • Un planeta pequeño no puede retener los gases en su atmósfera debido a un campo gravitacional débil.
Mercury
Mercury is in many ways similar to the Moon: its surface is heavily cratered and very old; it has no plate tectonics.
Mercury actually has a very thin atmosphere consisting of atoms blasted off its surface by the solar wind. Because Mercury is so hot, these atoms quickly escape into space. Thus in contrast to the Earth and Venus whose atmospheres are stable, Mercury's atmosphere is constantly being replenished.
Venus
Venus
Venus, the jewel of the sky, was once know by ancient astronomers as the morning star and evening star. Early astronomers once thought Venus to be two separate bodies. Venus, which is named after the Roman goddess of love and beauty, is veiled by thick swirling cloud cover. Astronomers refer to Venus as Earth's sister planet. Both are similar in size, mass, density and volume. Both formed about the same time and condensed out of the same nebula. However, during the last few years scientists have found that the kinship ends here. Venus is very different from the Earth. It has no oceans and is surrounded by a heavy atmosphere composed mainly of carbon dioxide with virtually no water vapor. Its clouds are composed of sulfuric acid droplets. At the surface, the atmospheric pressure is 92 times that of the Earth's at sea-level. Venus is scorched with a surface temperature of about 482° C (900° F). This high temperature is primarily due to a runaway greenhouse effect caused by the heavy atmosphere of carbon dioxide. Sunlight passes through the atmosphere to heat the surface of the planet. Heat is radiated out, but is trapped by the dense atmosphere and not allowed to escape into space. This makes Venus hotter than Mercury. A Venusian day is 243 Earth days and is longer than its year of 225 days. Oddly, Venus rotates from east to west. To an observer on Venus, the Sun would rise in the west and set in the east.
La Luna
No hay agua, no hay evidencia de agua en estado liquido en el pasado y no hay vida.
Mars Mars is the fourth planet from the Sun and is commonly referred to as the Red Planet. The rocks, soil and sky have a red or pink hue. The distinct red color was observed by stargazers throughout history. It was given its name by the Romans in honor of their god of war. Other civilizations have had similar names. The ancient Egyptians named the planet Her Descher meaning the red one. Before space exploration, Mars was considered the best candidate for harboring extraterrestrial life. Astronomers thought they saw straight lines crisscrossing its surface. This led to the popular belief that irrigation canals on the planet had been constructed by intelligent beings. In 1938, when Orson Welles broadcasted a radio drama based on the science fiction classic War of the Worlds by H.G. Wells, enough people believed in the tale of invading Martians to cause a near panic. Another reason for scientists to expect life on Mars had to do with the apparent seasonal color changes on the planet's surface. This phenomenon led to speculation that conditions might support a bloom of Martian vegetation during the warmer months and cause plant life to become dormant during colder periods.
Ophir Chasma is a large west-northwesttrending trough about 100 km wide. The Chasma is bordered by 4 km high walled cliffs, most likely faults, that show spurand-gully morphology and smooth sections. The walls have been dissected by landslides forming reentrants; one area (upper left) on the north wall shows a young landslide about 100 km wide. The volume of the landslide debris is more than 1000 times greater than that from the May 18, 1980 debris avalanche from Mount St. Helens. The longitudinal grooves seen in the foreground are thought to be due to differential shear and lateral spreading at high velocities. The landslide passes between mounds of interior layered deposits on the floor of the chasma. (Courtesy USGS)
No hay agua en estado liquido In July of 1965, Mariner 4, transmitted 22 close-up pictures of Mars. All that was revealed was a surface containing many craters and naturally occurring channels but no evidence of artificial canals or flowing water. Finally, in July and September 1976, Viking Landers 1 and 2 touched down on the surface of Mars. The three biology experiments aboard the landers discovered unexpected and enigmatic chemical activity in the Martian soil, but provided no clear evidence for the presence of living microorganisms in the soil near the landing sites. According to mission biologists, Mars is self-sterilizing. They believe the combination of solar ultraviolet radiation that saturates the surface, the extreme dryness of the soil and the oxidizing nature of the soil chemistry prevent the formation of living organisms in the Martian soil. The question of life on Mars at some time in the distant past remains open. Other instruments found no sign of organic chemistry at either landing site, but they did provide a precise and definitive analysis of the composition of the Martian atmosphere and found previously undetected trace elements.
Evidencia de canales naturales.
Atmosphere The atmosphere of Mars is quite different from that of Earth. It is composed primarily of carbon dioxide with small amounts of other gases. The six most common components of the atmosphere are: * * * * * *
Carbon Dioxide (CO2): 95.32% Nitrogen (N2): 2.7% Argon (Ar): 1.6% Oxygen (O2): 0.13% Water (H2O): 0.03% Neon (Ne): 0.00025 %
Martian air contains only about 1/1,000 as much water as our air, but even this small amount can condense out, forming clouds that ride high in the atmosphere or swirl around the slopes of towering volcanoes. Local patches of early morning fog can form in valleys. At the Viking Lander 2 site, a thin layer of water frost covered the ground each winter. There is evidence that in the past a denser martian atmosphere may have allowed water to flow on the planet. Physical features closely resembling shorelines, gorges, riverbeds and islands suggest that great rivers once marked the planet.
Temperature and Pressure The average recorded temperature on Mars is -63° C (-81° F) with a maximum temperature of 20° C (68° F) and a minimum of -140° C (-220° F).
Earth
EARTH Earth is the 3rd planet from the Sun at a distance of about 150 million kilometers (93.2 million miles). It takes 365.256 days for the Earth to travel around the Sun and 23.9345 hours for the Earth rotate a complete revolution. It has a diameter of 12,756 kilometers (7,973 miles), only a few hundred kilometers larger than that of Venus. Our atmosphere is composed of 78 percent nitrogen, 21 percent oxygen and 1 percent other constituents. Earth is the only planet in the solar system known to harbor life. Our planet's rapid spin and molten nickel-iron core give rise to an extensive magnetic field, which, along with the atmosphere, shields us from nearly all of the harmful radiation coming from the Sun and other stars. Earth's atmosphere protects us from meteors, most of which burn up before they can strike the surface. From our journeys into space, we have learned much about our home planet. The first American satellite, Explorer 1, discovered an intense radiation zone, now called the Van Allen radiation belts. This layer is formed from rapidly moving charged particles that are trapped by the Earth's magnetic field in a doughnut-shaped region surrounding the equator. Other findings from satellites show that our planet's magnetic field is distorted into a tear-drop shape by the solar wind. We also now know that our wispy upper atmosphere, once believed calm and uneventful, seethes with activity -- swelling by day and contracting by night. Affected by changes in solar activity, the upper atmosphere contributes to weather and climate on Earth
• El planeta Tierra tiene el tamaño adecuado; no se ha enfriado en su interior lo que resulta en actividad volcánica que lleva gases a la atmósfera continuamente. – Erupción volcánica en Kilauea, 50% vapor de agua
• También tiene, como resultado de su tamaño, una atmósfera que atrapa los gases (continuamente los gases escapan de nuestra atmósfera). • El planeta tierra se encuentra a una distancia adecuada del sol para que el agua se encuentre en sus estados sólido, liquido y gaseoso.
Reconstruyendo el origen de la Vida En nuestro planeta, una atmósfera primitiva bañada de luz ultravioleta del sol, resultaría en gases que se disolverían fácilmente en agua enriqueciendo el océano con carbón. Estos gases serian amonia (NH3), metano (CH4), y monóxido de carbono (CO).
Reconstruyendo el origen de la Vida • Uno de los productos químicos de la combinación de estos productos seria cianuro (HCN). • Este es uno de los bloques básicos en la construcción de moléculas orgánicas mas complejas.
Stanley Miller • Miller, en la Universidad de Chicago decidió reconstruir como seria una atmósfera primitiva para ver que reacciones químicas ocurren y sus resultados.
Miller, en un espacio sellado al Vació unió amonia (NH3), metano (CH4) e hidrogeno (H), e intento simular las condiciones de una atmósfera primitiva. Los calentó, condenso y añadió descargas eléctricas. El resultado de este experimento fue formaldehído, cianuro y otros cuatro aminoácidos- bloque fundamental la vida La mallor parte de los aminoácidos que se encuentran en las células hoy en día se peden haber formada en una atmósfera primitiva.
Spontaneous generation in a primeval soup: Miller's Experiment Stanley Miller, a graduate student in biochemistry, built the apparatus shown here. He filled it with * water (H2O * methane (CH4) * ammonia (NH3) and * hydrogen (H2) * but no oxygen He hypothesized that this mixture resembled the atmosphere of the early earth. (Some are not so sure.) The mixture was kept circulating by continuously boiling and then condensing the water. The gases passed through a chamber containing two electrodes with a spark passing between them. At the end of a week, Miller used paper chromatography to show that the flask now contained several amino acids as well as some other organic molecules. In the years since Miller's work, many variants of his procedure have been tried. Virtually all the small molecules that are associated with life have been formed: * all the amino acids used in protein synthesis * all the purines and pyrimidines used in nucleic acid synthesis.
