When considering the kind of experience that makes life better, most people first think that happiness consists in experiencing pleasure: good food, all the comforts that money can buy. We imagine the satisfaction of traveling to exciting places or being surrounded by expensive devices. If we cannot afford those goals, then we are happy to settle for a quiet evening in front of the television set with a drink close by.

Pleasure is a feeling of contentment that one achieves whenever expectations set by biological programs or by social conditioning have been met. The taste of food when we are hungry is pleasant because it reduces a physiological (生理的) imbalance. Resting in the evening while passively absorbing information from TV, with alcohol or drugs to dull the mind overexcited by the demands of work, is pleasantly relaxing. Traveling to Acapulco is pleasant because the exciting novelty (新奇) restores our sensations (感觉) exhausted by the repetitive routines of everyday life.

When people think further about what makes their lives rewarding, they tend to move beyond pleasant memories and begin to remember other events, other experiences that overlap (重叠) with pleasurable ones but fall into a category that deserves a separate name: enjoyment. Enjoyable events occur when a person has not only met some expectation or satisfied a need or a desire but also gone beyond what he or she has been programmed to do and achieved something unexpected, perhaps something even unimagined before.

Enjoyment is characterized by this forward movement: by a sense of novelty, of accomplishment. Playing a close game of tennis that stretches one’s ability is enjoyable, as is reading a book that reveals things in a new light, as is having a conversation that leads us to express ideas we didn’t know we had. Closing a contested business deal, or any piece of work well done, is enjoyable. None of these experiences may be particularly pleasurable at the time they are taking place, but afterward we think back on them and say, “That really was fun” and wish they would happen again. After an enjoyable event we know that we have changed, that our self has grown: in some respect, we have become more complex as a result of it.

Experiences that give pleasure can also give enjoyment, but the two sensations are quite different. For instance, everybody takes pleasure in eating. To enjoy food, however, is more difficult. A gourmet (美食家) enjoys eating, as does anyone who pays enough attention to a meal so as to discriminate the various sensations provided by it. As this example suggests, we can experience pleasure without any investment of psychic energy, whereas enjoyment happens only as a result of unusual investments of attention. A person can feel pleasure without any effort, but it is impossible to enjoy a tennis game, a book, or a conversation unless attention is fully concentrated on the activity.

You improve your robot’s software by improving its software. Agrim Gupta of Stanford University, however, begs to differ. He thinks you can also improve a robot’s software by improving its hardware. He and his colleagues have invented a way of testing this idea.

They brought to their robots, unimals, the principles of evolution (进化) by natural selection. Unimals, with globes for heads and sticks for arms and legs, are software beings interacting with a virtual environment. The environments where they wandered were in three varieties: flat grounds, grounds with hills and steps, and ones that had the complexities of the second sort, but with added objects.

To begin with, the unimals were randomly assigned various shapes, but with identical software— derl. Newly created unimals learned to face the challenges in a virtual bootcamp. They were then entered into tournaments in groups. Each group winner was awarded one mutation (变异) —one extra arm or leg, or one extra turning in a joint. The new replaced the oldest unimal and then was assigned to a new group, and the process repeated. About 4,000 varieties of them underwent training.

The team were surprised by the diversity of shapes that evolved. Crucially, though, the researchers found the most successful unimals learned tasks in half the time their oldest ancestors had taken, and that those evolving in the toughest grounds were the most successful.

In this evolution of unimals’ morphology (形态) to promote the ability to learn, Dr Gupta sees a version of something called the Baldwin effect. In 1896 James Baldwin, a psychologist, argued that minds evolve to make the best use of the morphologies of the bodies. What Dr Gupta has shown, though in software, is that the opposite can also be true — changes in body morphology can improve the way minds work. Even though he held the software constant, it became more efficient at learning as the unimals’ bodies evolved.

Whether that discovery can be turned to account in the way robots are developed remains to be seen. But the way of testing is certainly an out-of-the-box idea.

Not so long ago, most scientists thought of Mars as dead and cold. But, as we previously reported, microbes (微生物) could be hiding beneath the red planet's surface, kept warm by its core and fed by radiation from rocks. A recent study shows that Mars might have experienced volcanic explosions 50,000 years ago- practically last week in geologic time (地质时期). Such activity raises the possibility that, volcanically, Mars “may still be active, even today,” says David Horvath, a scientist at the Planetary Science Institute in Tucson, Arizona.

What's more, NASA's InSight mission has picked up Marsquakes coming from the area Horvath studied. The quakes suggest there could still be molten magma (熔化的岩浆) below the surface, warming the frozen underground and making liquid water possible around volcanic hotspots, Horvath says. That could create an underground haven for life on Mars.

The team, based out of the University of Arizona, looked at a single fissure (裂缝), one of several fissures in the ground known collectively as the Cerberus Fossae. They found it surrounded by a dark region which they think is ash (灰) from a volcanic eruption. The fissures stretch across the Martian surface for miles, although they're fairly shallow. The one in question is only about 20 meters deep. They focused on this particular fissure because it stands out. It’ s surrounded by visibly dark material which keeps heat well, Horvath says.

If Mars was volcanically active, though, it's not impossible that life could be hanging out in little underground islands around the larger Martian volcanoes. If volcanoes on Mars are similar to those on Earth, they could have been active for millions of years, says Erika Rader, a volcanologist at the University of Idaho. But it's still a very extreme environment. By contrast, one deep underground fed by radiation would probably be more stable, she says. How about the possibility of current volcanic activity on Mars? “I want it to be true,” Rader says. “But this paper alone would not convince me of that.”