Getting closer to the neighbour

Three Mars missions, from the US, China and the United Arab Emirates (UAE) are due to launch in July. The US and China are established space going nations, but it is the UAE’s first interplanetary mission.

These missions will seek to establish if life existed sometime in the past on the red planet. The simultaneous launches are driven by astronomical imperatives. At their closest, Earth and Mars are “only” 55 million km apart. The two planets are more than 400 million mm apart at the furthest.

The easiest way to understand this, is to think of pizzas. Planetary orbits are pizza-shaped, or elliptical. The “slices” of the pizza are equal in size. That is, equal areas are swept out by a given orbit in equal time periods. (Planets move faster when closer to the sun).

Some orbits are more circular in shape, others more “eccentric”. Mars has a larger orbit than Earth being further from the sun, and it’s also more eccentric. Every 26 months or so, there is a window of a few weeks when Mars and Earth are in ideal alignment. A launch then minimises fuel consumption and travel time. Even so, it is a long journey of about seven months.

The UAE spacecraft, Amal, was designed and built in consultation with the University of Colorado. It is due to launch from Japan and scheduled to reach in early 2021 to commemorate the founding of the UAE in 1971. The mission control will be done from Dubai. Amal is supposed to study the tenuous Martian upper atmosphere and monitor climate changes.  

China launches next week. The Tianwen Mission includes both an orbiter and lander. China hasn’t released much detail on the mission objectives. Nasa’s Perseverance is scheduled to launch in end-July and it will land in the unexplored Jezero Crater, which is probably a dried up river delta. This is an ambitious landing site since it’s a rocky area with cliffs and dunes. A new guidance system and landing gear with parachutes will be deployed along with a 2 kilogram helicopter.   

Orbiting mars is a comparatively easy process. But Mars landings have to be completely autonomous and they’re referred to as “seven minutes of terror”. First, the craft is put into orbit. Then the lander is detached and heads for touchdown.

A radio signal from Earth to Mars and back takes a minimum of about seven minutes when the two planets are at their closest. There is no question of monitoring a mission in real-time, let alone remote control. Even in the era of AI, this sort of autonomous manoeuvring is a challenge.  

There are six craft currently in orbit around Mars, including India’s Mangalyaan, three Nasa craft and two Euro Space Agency orbiters. Only the US has successfully landed on Mars, as many as eight times, starting with the Viking Missions in 1976. The Nasa landers, InSight and Curiosity, are both currently operational and Perseverance would join them.

Mars and Earth are respectively the third and fourth planets orbiting the sun and both are rocky balls. But the similarities end there. Mars is smaller with a gravity only 38 per cent that of Earth. It has a very thin atmosphere, which is bleeding off because it has a very weak magnetic field. Earth’s strong magnetic field blocks solar radiation, and higher gravity, also ensures the atmosphere remains intact. Mars lost its magnetic field millions of years ago. Solar radiation or “wind” as it’s called consists of highly charged particles. The wind constantly ionises the Mars atmosphere and it is gradually stripped since the charged atmospheric particles bleed off into space. The loss of atmosphere has also led to loss of liquid surface water though Mars has polar ice-caps. Surface temperatures seem to range from 20 °C to minus 150 °C.

The Martian surface shows there were oceans and rivers in the dim-distant past and there may be liquid water trapped below the surface even now. Indeed, this would be something the landers will try to discover. Exploration is a huge task. Although the Earth is larger, roughly 80 per cent of the surface is covered by water. The Martian landscape is completely exposed, and the surface area is therefore as large as the Earth’s dry areas.

In an era of liquid water and thicker atmosphere, there could have been life. Perseverance will hunt for biological signatures, drilling rocks to collect samples. The lander-rover will also use radar to probe for sub-surface water. The rover will also crack carbon dioxide to produce oxygen.

These technology demonstrations would be vital for a manned mission sometime in the 2030s. This will be an incredible challenge. Astronauts would have to travel seven months, spend 26 months in very strange, hostile conditions and then return in a seven month journey.

 


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